64638691 has 4 divisors (see below), whose sum is σ = 69610912. Its totient is φ = 59666472.

The previous prime is 64638661. The next prime is 64638697. The reversal of 64638691 is 19683646.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19683646 = 2 ⋅9841823.

It is a cyclic number.

It is not a de Polignac number, because 64638691 - 2⁵ = 64638659 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (64638697) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2486091 + ... + 2486116.

It is an arithmetic number, because the mean of its divisors is an integer number (17402728).

Almost surely, 2^64638691 is an apocalyptic number.

64638691 is a deficient number, since it is larger than the sum of its proper divisors (4972221).

64638691 is a wasteful number, since it uses less digits than its factorization.

64638691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4972220.

The product of its digits is 186624, while the sum is 43.

The square root of 64638691 is about 8039.8190900045. The cubic root of 64638691 is about 401.3262043456.

The spelling of 64638691 in words is "sixty-four million, six hundred thirty-eight thousand, six hundred ninety-one".