64507991 has 2 divisors, whose sum is σ = 64507992. Its totient is φ = 64507990.

The previous prime is 64507987. The next prime is 64508009. The reversal of 64507991 is 19970546.

64507991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 64507991 - 2² = 64507987 is a prime.

It is a super-2 number, since 2×64507991² = 8322561805712162, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (64507901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 32253995 + 32253996.

It is an arithmetic number, because the mean of its divisors is an integer number (32253996).

Almost surely, 2^64507991 is an apocalyptic number.

64507991 is a deficient number, since it is larger than the sum of its proper divisors (1).

64507991 is an equidigital number, since it uses as much as digits as its factorization.

64507991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 68040, while the sum is 41.

The square root of 64507991 is about 8031.6866846261. The cubic root of 64507991 is about 401.0555267913.

It can be divided in two parts, 6450 and 7991, that added together give a palindrome (14441).

The spelling of 64507991 in words is "sixty-four million, five hundred seven thousand, nine hundred ninety-one".