2129400

Appears in sequences

• Unitary superperfect numbers: numbers n such that usigma(usigma(n)) = 2*n, where usigma(n) is the sum of unitary divisors of n (A034448).at n=17A038843
• Composite numbers k such that k - phi(k) divides sigma(k) - k.at n=29A068418
• Composite n such that n reduced mod(phi(n)) = sigma(n) reduced mod(n).at n=28A068495