64691639 has 2 divisors, whose sum is σ = 64691640. Its totient is φ = 64691638.

The previous prime is 64691629. The next prime is 64691657. The reversal of 64691639 is 93619646.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 64691639 - 2⁴ = 64691623 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 64691639.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (64691629) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 32345819 + 32345820.

It is an arithmetic number, because the mean of its divisors is an integer number (32345820).

Almost surely, 2^64691639 is an apocalyptic number.

64691639 is a deficient number, since it is larger than the sum of its proper divisors (1).

64691639 is an equidigital number, since it uses as much as digits as its factorization.

64691639 is an evil number, because the sum of its binary digits is even.

The product of its digits is 209952, while the sum is 44.

The square root of 64691639 is about 8043.1112761170. Note that the first 3 decimals coincide. The cubic root of 64691639 is about 401.4357549368.

The spelling of 64691639 in words is "sixty-four million, six hundred ninety-one thousand, six hundred thirty-nine".