644686499 has 2 divisors, whose sum is σ = 644686500. Its totient is φ = 644686498.

The previous prime is 644686439. The next prime is 644686519. The reversal of 644686499 is 994686446.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 644686499 - 2²⁰ = 643637923 is a prime.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (644686429) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322343249 + 322343250.

It is an arithmetic number, because the mean of its divisors is an integer number (322343250).

Almost surely, 2^644686499 is an apocalyptic number.

644686499 is a deficient number, since it is larger than the sum of its proper divisors (1).

644686499 is an equidigital number, since it uses as much as digits as its factorization.

644686499 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8957952, while the sum is 56.

The square root of 644686499 is about 25390.6774033305. The cubic root of 644686499 is about 863.8722532573.

The spelling of 644686499 in words is "six hundred forty-four million, six hundred eighty-six thousand, four hundred ninety-nine".