638690 has 32 divisors (see below), whose sum is σ = 1315440. Its totient is φ = 221952.

The previous prime is 638689. The next prime is 638699. The reversal of 638690 is 96836.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 185761 + 452929 = 431^2 + 673^2 .

It is a super-2 number, since 2×638690² = 815849832200, which contains 22 as substring.

It is an Ulam number.

It is not an unprimeable number, because it can be changed into a prime (638699) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 37562 + ... + 37578.

2⁶³⁸⁶⁹⁰ is an apocalyptic number.

638690 is an abundant number, since it is smaller than the sum of its proper divisors (676750).

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

638690 is a wasteful number, since it uses less digits than its factorization.

638690 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 71 (or 37 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 32.

The square root of 638690 is about 799.1808306009. The cubic root of 638690 is about 86.1185493247.

The spelling of 638690 in words is "six hundred thirty-eight thousand, six hundred ninety".