21087400 has 24 divisors (see below), whose sum is σ = 49028670. Its totient is φ = 8434880.

The previous prime is 21087377. The next prime is 21087401. The reversal of 21087400 is 478012.

It can be written as a sum of positive squares in 3 ways, for example, as 9622404 + 11464996 = 3102^2 + 3386^2 .

It is not an unprimeable number, because it can be changed into a prime (21087401) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 52519 + ... + 52918.

Almost surely, 2^21087400 is an apocalyptic number.

21087400 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21087400 is an abundant number, since it is smaller than the sum of its proper divisors (27941270).

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

21087400 is a wasteful number, since it uses less digits than its factorization.

21087400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 105453 (or 105444 counting only the distinct ones).

The product of its (nonzero) digits is 448, while the sum is 22.

The square root of 21087400 is about 4592.1019152453. The cubic root of 21087400 is about 276.2746338672.

The spelling of 21087400 in words is "twenty-one million, eighty-seven thousand, four hundred".