638629956 has 36 divisors (see below), whose sum is σ = 1709275932. Its totient is φ = 200354304.

The previous prime is 638629949. The next prime is 638629961. The reversal of 638629956 is 659926836.

638629956 is a `hidden beast` number, since 6 + 3 + 8 + 629 + 9 + 5 + 6 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 388484100 + 250145856 = 19710^2 + 15816^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 521145 + ... + 522368.

It is an arithmetic number, because the mean of its divisors is an integer number (47479887).

Almost surely, 2^638629956 is an apocalyptic number.

It is an amenable number.

638629956 is an abundant number, since it is smaller than the sum of its proper divisors (1070645976).

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

638629956 is a wasteful number, since it uses less digits than its factorization.

638629956 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1043540 (or 1043535 counting only the distinct ones).

The product of its digits is 4199040, while the sum is 54.

The square root of 638629956 is about 25271.1289023660. The cubic root of 638629956 is about 861.1585053802.

The spelling of 638629956 in words is "six hundred thirty-eight million, six hundred twenty-nine thousand, nine hundred fifty-six".