640218986 has 16 divisors (see below), whose sum is σ = 1056293568. Its totient is φ = 291007420.

The previous prime is 640218983. The next prime is 640219009. The reversal of 640218986 is 689812046.

It is a happy number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (640218983) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 117590 + ... + 122913.

It is an arithmetic number, because the mean of its divisors is an integer number (66018348).

Almost surely, 2^640218986 is an apocalyptic number.

640218986 is a deficient number, since it is larger than the sum of its proper divisors (416074582).

640218986 is a wasteful number, since it uses less digits than its factorization.

640218986 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 240538 (or 240516 counting only the distinct ones).

The product of its (nonzero) digits is 165888, while the sum is 44.

The square root of 640218986 is about 25302.5490020274. The cubic root of 640218986 is about 861.8721546034.

The spelling of 640218986 in words is "six hundred forty million, two hundred eighteen thousand, nine hundred eighty-six".