644626867 has 2 divisors, whose sum is σ = 644626868. Its totient is φ = 644626866.

The previous prime is 644626849. The next prime is 644626883. The reversal of 644626867 is 768626446.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644626867 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 644626867.

It is not a weakly prime, because it can be changed into another prime (644626897) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322313433 + 322313434.

It is an arithmetic number, because the mean of its divisors is an integer number (322313434).

Almost surely, 2^644626867 is an apocalyptic number.

644626867 is a deficient number, since it is larger than the sum of its proper divisors (1).

644626867 is an equidigital number, since it uses as much as digits as its factorization.

644626867 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2322432, while the sum is 49.

The square root of 644626867 is about 25389.5030869058. The cubic root of 644626867 is about 863.8456170454.

The spelling of 644626867 in words is "six hundred forty-four million, six hundred twenty-six thousand, eight hundred sixty-seven".