646440637 has 2 divisors, whose sum is σ = 646440638. Its totient is φ = 646440636.

The previous prime is 646440611. The next prime is 646440659. The reversal of 646440637 is 736044646.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 511392996 + 135047641 = 22614^2 + 11621^2 .

It is a cyclic number.

It is not a de Polignac number, because 646440637 - 2²³ = 638052029 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 646440637.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (646440937) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 323220318 + 323220319.

It is an arithmetic number, because the mean of its divisors is an integer number (323220319).

Almost surely, 2^646440637 is an apocalyptic number.

It is an amenable number.

646440637 is a deficient number, since it is larger than the sum of its proper divisors (1).

646440637 is an equidigital number, since it uses as much as digits as its factorization.

646440637 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 290304, while the sum is 40.

The square root of 646440637 is about 25425.1968920597. The cubic root of 646440637 is about 864.6550517397.

The spelling of 646440637 in words is "six hundred forty-six million, four hundred forty thousand, six hundred thirty-seven".