640697904 has 480 divisors, whose sum is σ = 2469841920. Its totient is φ = 155105280.

The previous prime is 640697903. The next prime is 640697923. The reversal of 640697904 is 409796046.

It is a self number, because there is not a number n which added to its sum of digits gives 640697904.

It is not an unprimeable number, because it can be changed into a prime (640697903) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 6220317 + ... + 6220419.

It is an arithmetic number, because the mean of its divisors is an integer number (5145504).

Almost surely, 2^640697904 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640697904, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1234920960).

640697904 is an abundant number, since it is smaller than the sum of its proper divisors (1829144016).

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

640697904 is a wasteful number, since it uses less digits than its factorization.

640697904 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 166 (or 143 counting only the distinct ones).

The product of its (nonzero) digits is 326592, while the sum is 45.

The square root of 640697904 is about 25312.0110619445. The cubic root of 640697904 is about 862.0870098413.

It can be divided in two parts, 640697 and 904, that added together give a square (641601 = 801²).

The spelling of 640697904 in words is "six hundred forty million, six hundred ninety-seven thousand, nine hundred four".