21387400 has 24 divisors (see below), whose sum is σ = 49726170. Its totient is φ = 8554880.

The previous prime is 21387391. The next prime is 21387403. The reversal of 21387400 is 478312.

It can be written as a sum of positive squares in 3 ways, for example, as 14945956 + 6441444 = 3866^2 + 2538^2 .

It is a Harshad number since it is a multiple of its sum of digits (25).

It is not an unprimeable number, because it can be changed into a prime (21387403) 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, 53269 + ... + 53668.

Almost surely, 2^21387400 is an apocalyptic number.

21387400 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21387400 is an abundant number, since it is smaller than the sum of its proper divisors (28338770).

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

21387400 is a wasteful number, since it uses less digits than its factorization.

21387400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 106953 (or 106944 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 25.

The square root of 21387400 is about 4624.6513382092. The cubic root of 21387400 is about 277.5786104158.

The spelling of 21387400 in words is "twenty-one million, three hundred eighty-seven thousand, four hundred".