638691552 has 72 divisors (see below), whose sum is σ = 1850592744. Its totient is φ = 208875264.

The previous prime is 638691541. The next prime is 638691569. The reversal of 638691552 is 255196836.

638691552 is a `hidden beast` number, since 6 + 3 + 8 + 6 + 91 + 552 = 666.

It is a tau number, because it is divible by the number of its divisors (72).

It is a junction number, because it is equal to n+sod(n) for n = 638691498 and 638691507.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5658 + ... + 36185.

It is an arithmetic number, because the mean of its divisors is an integer number (25702677).

Almost surely, 2^638691552 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 638691552, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (925296372).

638691552 is an abundant number, since it is smaller than the sum of its proper divisors (1211901192).

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

638691552 is a wasteful number, since it uses less digits than its factorization.

638691552 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41912 (or 41901 counting only the distinct ones).

The product of its digits is 388800, while the sum is 45.

The square root of 638691552 is about 25272.3475759574. The cubic root of 638691552 is about 861.1861907993.

The spelling of 638691552 in words is "six hundred thirty-eight million, six hundred ninety-one thousand, five hundred fifty-two".