21438504 has 24 divisors (see below), whose sum is σ = 58062810. Its totient is φ = 7146144.

The previous prime is 21438499. The next prime is 21438541. The reversal of 21438504 is 40583412.

It can be written as a sum of positive squares in only one way, i.e., 21178404 + 260100 = 4602^2 + 510^2 .

It is a tau number, because it is divible by the number of its divisors (24).

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 148807 + ... + 148950.

Almost surely, 2^21438504 is an apocalyptic number.

21438504 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21438504 is an abundant number, since it is smaller than the sum of its proper divisors (36624306).

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

21438504 is a wasteful number, since it uses less digits than its factorization.

21438504 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 297769 (or 297762 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 27.

The square root of 21438504 is about 4630.1732149024. The cubic root of 21438504 is about 277.7995207632.

The spelling of 21438504 in words is "twenty-one million, four hundred thirty-eight thousand, five hundred four".