21387039 has 16 divisors (see below), whose sum is σ = 29327232. Its totient is φ = 13855968.

The previous prime is 21387001. The next prime is 21387059. The reversal of 21387039 is 93078312.

It is not a de Polignac number, because 21387039 - 2¹¹ = 21384991 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21387059) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 40632 + ... + 41154.

It is an arithmetic number, because the mean of its divisors is an integer number (1832952).

Almost surely, 2^21387039 is an apocalyptic number.

21387039 is a deficient number, since it is larger than the sum of its proper divisors (7940193).

21387039 is a wasteful number, since it uses less digits than its factorization.

21387039 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 886.

The product of its (nonzero) digits is 9072, while the sum is 33.

The square root of 21387039 is about 4624.6123080751. The cubic root of 21387039 is about 277.5770486483.

The spelling of 21387039 in words is "twenty-one million, three hundred eighty-seven thousand, thirty-nine".