644613623 has 2 divisors, whose sum is σ = 644613624. Its totient is φ = 644613622.

The previous prime is 644613587. The next prime is 644613649. The reversal of 644613623 is 326316446.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 644613623 - 2⁸ = 644613367 is a prime.

It is a super-2 number, since 2×644613623² = 831053445914372258, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644613523) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322306811 + 322306812.

It is an arithmetic number, because the mean of its divisors is an integer number (322306812).

Almost surely, 2^644613623 is an apocalyptic number.

644613623 is a deficient number, since it is larger than the sum of its proper divisors (1).

644613623 is an equidigital number, since it uses as much as digits as its factorization.

644613623 is an evil number, because the sum of its binary digits is even.

The product of its digits is 62208, while the sum is 35.

The square root of 644613623 is about 25389.2422691186. The cubic root of 644613623 is about 863.8397010391.

The spelling of 644613623 in words is "six hundred forty-four million, six hundred thirteen thousand, six hundred twenty-three".