638439740 has 12 divisors (see below), whose sum is σ = 1340723496. Its totient is φ = 255375888.

The previous prime is 638439731. The next prime is 638439757. The reversal of 638439740 is 47934836.

It is a happy number.

It is a super-2 number, since 2×638439740² = 815210603222535200, which contains 22 as substring.

It is a zygodrome in base 3.

It is a junction number, because it is equal to n+sod(n) for n = 638439691 and 638439700.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15960974 + ... + 15961013.

It is an arithmetic number, because the mean of its divisors is an integer number (111726958).

Almost surely, 2^638439740 is an apocalyptic number.

It is an amenable number.

638439740 is an abundant number, since it is smaller than the sum of its proper divisors (702283756).

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

638439740 is a wasteful number, since it uses less digits than its factorization.

638439740 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31921996 (or 31921994 counting only the distinct ones).

The product of its (nonzero) digits is 435456, while the sum is 44.

The square root of 638439740 is about 25267.3651178749. The cubic root of 638439740 is about 861.0729981729.

The spelling of 638439740 in words is "six hundred thirty-eight million, four hundred thirty-nine thousand, seven hundred forty".