644536402 has 16 divisors (see below), whose sum is σ = 1033072920. Its totient is φ = 300526848.

The previous prime is 644536363. The next prime is 644536423. The reversal of 644536402 is 204635446.

It can be written as a sum of positive squares in 4 ways, for example, as 623550841 + 20985561 = 24971^2 + 4581^2 .

It is a Harshad number since it is a multiple of its sum of digits (34).

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 83253 + ... + 90664.

Almost surely, 2^644536402 is an apocalyptic number.

644536402 is a deficient number, since it is larger than the sum of its proper divisors (388536518).

644536402 is a wasteful number, since it uses less digits than its factorization.

644536402 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 174045.

The product of its (nonzero) digits is 69120, while the sum is 34.

The square root of 644536402 is about 25387.7214810625. The cubic root of 644536402 is about 863.8052053211.

The spelling of 644536402 in words is "six hundred forty-four million, five hundred thirty-six thousand, four hundred two".