13645088

Appears in sequences

• Numbers of the form 2*k^2 such that sigma(2*k^2) is an odd square.at n=2A074388
• Numbers n such that both sigma(n) and sigma(sigma(n)) are odd numbers.at n=8A097025
• Sigma-powerful numbers: powerful numbers n such that sigma(n) is also powerful. An incomplete version of A337045.at n=5A180090
• Numbers k such that both k and sigma(k)=A000203(k) are powerful, i.e., are terms of A001694.at n=19A337044
• Indecomposable sigma-powerful numbers: powerful numbers k such that sigma(k) is also powerful, but restricted to terms that are not the product of 2 terms > 1 of A337044.at n=13A337045