401556691 has 2 divisors, whose sum is σ = 401556692. Its totient is φ = 401556690.

The previous prime is 401556667. The next prime is 401556703. The reversal of 401556691 is 196655104.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 401556691 - 2¹⁹ = 401032403 is a prime.

It is a super-2 number, since 2×401556691² = 322495552173738962, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 401556691.

It is not a weakly prime, because it can be changed into another prime (401554691) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 200778345 + 200778346.

It is an arithmetic number, because the mean of its divisors is an integer number (200778346).

Almost surely, 2^401556691 is an apocalyptic number.

401556691 is a deficient number, since it is larger than the sum of its proper divisors (1).

401556691 is an equidigital number, since it uses as much as digits as its factorization.

401556691 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 32400, while the sum is 37.

The square root of 401556691 is about 20038.8794846418. The cubic root of 401556691 is about 737.7608789225.

It can be divided in two parts, 4015 and 56691, that added together give a palindrome (60706).

The spelling of 401556691 in words is "four hundred one million, five hundred fifty-six thousand, six hundred ninety-one".