644963890 has 16 divisors (see below), whose sum is σ = 1182840408. Its totient is φ = 253117696.

The previous prime is 644963887. The next prime is 644963903. The reversal of 644963890 is 98369446.

644963890 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 634485721 + 10478169 = 25189^2 + 3237^2 .

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, 607927 + ... + 608986.

Almost surely, 2^644963890 is an apocalyptic number.

644963890 is a deficient number, since it is larger than the sum of its proper divisors (537876518).

644963890 is a wasteful number, since it uses less digits than its factorization.

644963890 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1216973.

The product of its (nonzero) digits is 1119744, while the sum is 49.

The square root of 644963890 is about 25396.1392735195. The cubic root of 644963890 is about 863.9961357066.

It can be divided in two parts, 64496 and 3890, that added together give a palindrome (68386).

The spelling of 644963890 in words is "six hundred forty-four million, nine hundred sixty-three thousand, eight hundred ninety".