399725777981 has 2 divisors, whose sum is σ = 399725777982. Its totient is φ = 399725777980.

The previous prime is 399725777953. The next prime is 399725778043. The reversal of 399725777981 is 189777527993.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 204154867225 + 195570910756 = 451835^2 + 442234^2 .

It is a cyclic number.

It is not a de Polignac number, because 399725777981 - 2³⁸ = 124847871037 is a prime.

It is a super-2 number, since 2×399725777981² (a number of 24 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 399725777899 and 399725777908.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (399725777951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 199862888990 + 199862888991.

It is an arithmetic number, because the mean of its divisors is an integer number (199862888991).

Almost surely, 2^399725777981 is an apocalyptic number.

It is an amenable number.

399725777981 is a deficient number, since it is larger than the sum of its proper divisors (1).

399725777981 is an equidigital number, since it uses as much as digits as its factorization.

399725777981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 420078960, while the sum is 74.

The spelling of 399725777981 in words is "three hundred ninety-nine billion, seven hundred twenty-five million, seven hundred seventy-seven thousand, nine hundred eighty-one".