21387750 has 32 divisors (see below), whose sum is σ = 53385696. Its totient is φ = 5703200.

The previous prime is 21387733. The next prime is 21387757. The reversal of 21387750 is 5778312.

It is a hoax number, since the sum of its digits (33) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21387757) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13509 + ... + 15008.

It is an arithmetic number, because the mean of its divisors is an integer number (1668303).

Almost surely, 2^21387750 is an apocalyptic number.

21387750 is an abundant number, since it is smaller than the sum of its proper divisors (31997946).

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

21387750 is a wasteful number, since it uses less digits than its factorization.

21387750 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28537 (or 28527 counting only the distinct ones).

The product of its (nonzero) digits is 11760, while the sum is 33.

The square root of 21387750 is about 4624.6891787449. The cubic root of 21387750 is about 277.5801245781.

The spelling of 21387750 in words is "twenty-one million, three hundred eighty-seven thousand, seven hundred fifty".