401565991 has 2 divisors, whose sum is σ = 401565992. Its totient is φ = 401565990.

The previous prime is 401565973. The next prime is 401566019. The reversal of 401565991 is 199565104.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 401565991 - 2²⁵ = 368011559 is a prime.

It is a super-3 number, since 3×401565991³ (a number of 27 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (401565911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 200782995 + 200782996.

It is an arithmetic number, because the mean of its divisors is an integer number (200782996).

Almost surely, 2^401565991 is an apocalyptic number.

401565991 is a deficient number, since it is larger than the sum of its proper divisors (1).

401565991 is an equidigital number, since it uses as much as digits as its factorization.

401565991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 48600, while the sum is 40.

The square root of 401565991 is about 20039.1115322012. Note that the first 3 decimals coincide. The cubic root of 401565991 is about 737.7665743601.

The spelling of 401565991 in words is "four hundred one million, five hundred sixty-five thousand, nine hundred ninety-one".