21437540 has 24 divisors (see below), whose sum is σ = 45255672. Its totient is φ = 8529920.

The previous prime is 21437531. The next prime is 21437573. The reversal of 21437540 is 4573412.

It can be written as a sum of positive squares in 4 ways, for example, as 10201636 + 11235904 = 3194^2 + 3352^2 .

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 7 ways as a sum of consecutive naturals, for example, 1220 + ... + 6660.

It is an arithmetic number, because the mean of its divisors is an integer number (1885653).

Almost surely, 2^21437540 is an apocalyptic number.

21437540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21437540 is an abundant number, since it is smaller than the sum of its proper divisors (23818132).

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

21437540 is a wasteful number, since it uses less digits than its factorization.

21437540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5647 (or 5645 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 26.

The square root of 21437540 is about 4630.0691139550. The cubic root of 21437540 is about 277.7953568727.

The spelling of 21437540 in words is "twenty-one million, four hundred thirty-seven thousand, five hundred forty".