21015959 has 4 divisors (see below), whose sum is σ = 21030504. Its totient is φ = 21001416.

The previous prime is 21015947. The next prime is 21015971. The reversal of 21015959 is 95951012.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (21015947) and next prime (21015971).

It is a cyclic number.

It is not a de Polignac number, because 21015959 - 2⁸ = 21015703 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011959) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4832 + ... + 8085.

It is an arithmetic number, because the mean of its divisors is an integer number (5257626).

Almost surely, 2^21015959 is an apocalyptic number.

21015959 is a deficient number, since it is larger than the sum of its proper divisors (14545).

21015959 is a wasteful number, since it uses less digits than its factorization.

21015959 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14544.

The product of its (nonzero) digits is 4050, while the sum is 32.

The square root of 21015959 is about 4584.3166339161. The cubic root of 21015959 is about 275.9622883082.

The spelling of 21015959 in words is "twenty-one million, fifteen thousand, nine hundred fifty-nine".