640838961 has 24 divisors (see below), whose sum is σ = 1060098624. Its totient is φ = 365430240.

The previous prime is 640838959. The next prime is 640838981. The reversal of 640838961 is 169838046.

It is not a de Polignac number, because 640838961 - 2¹ = 640838959 is a prime.

It is not an unprimeable number, because it can be changed into a prime (640838941) 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, 20575 + ... + 41291.

It is an arithmetic number, because the mean of its divisors is an integer number (44170776).

Almost surely, 2^640838961 is an apocalyptic number.

It is an amenable number.

640838961 is a deficient number, since it is larger than the sum of its proper divisors (419259663).

640838961 is a wasteful number, since it uses less digits than its factorization.

640838961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21221 (or 21218 counting only the distinct ones).

The product of its (nonzero) digits is 248832, while the sum is 45.

The square root of 640838961 is about 25314.7972735315. The cubic root of 640838961 is about 862.1502713168.

It can be divided in two parts, 6408 and 38961, that added together give a square (45369 = 213²).

The spelling of 640838961 in words is "six hundred forty million, eight hundred thirty-eight thousand, nine hundred sixty-one".