640690944 has 216 divisors, whose sum is σ = 1898957760. Its totient is φ = 191195136.

The previous prime is 640690943. The next prime is 640690957. The reversal of 640690944 is 449096046.

It is a super-2 number, since 2×640690944² = 820969771447222272, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 640690896 and 640690905.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640690943) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 7719127 + ... + 7719209.

Almost surely, 2^640690944 is an apocalyptic number.

640690944 is a gapful number since it is divisible by the number (64) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640690944, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (949478880).

640690944 is an abundant number, since it is smaller than the sum of its proper divisors (1258266816).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

640690944 is a wasteful number, since it uses less digits than its factorization.

640690944 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 167 (or 130 counting only the distinct ones).

The product of its (nonzero) digits is 186624, while the sum is 42.

The square root of 640690944 is about 25311.8735774340. The cubic root of 640690944 is about 862.0838881686.

The spelling of 640690944 in words is "six hundred forty million, six hundred ninety thousand, nine hundred forty-four".