640947870 has 64 divisors (see below), whose sum is σ = 1726885440. Its totient is φ = 169150464.

The previous prime is 640947863. The next prime is 640947887. The reversal of 640947870 is 78749046.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 13954 + ... + 38426.

It is an arithmetic number, because the mean of its divisors is an integer number (26982585).

Almost surely, 2^640947870 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640947870, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (863442720).

640947870 is an abundant number, since it is smaller than the sum of its proper divisors (1085937570).

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

640947870 is a wasteful number, since it uses less digits than its factorization.

640947870 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24586 (or 24580 counting only the distinct ones).

The product of its (nonzero) digits is 338688, while the sum is 45.

The square root of 640947870 is about 25316.9482758092. The cubic root of 640947870 is about 862.1991086540.

The spelling of 640947870 in words is "six hundred forty million, nine hundred forty-seven thousand, eight hundred seventy".