21902015 has 4 divisors (see below), whose sum is σ = 26282424. Its totient is φ = 17521608.

The previous prime is 21901993. The next prime is 21902029. The reversal of 21902015 is 51020912.

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

It is a cyclic number.

It is not a de Polignac number, because 21902015 - 2¹⁴ = 21885631 is a prime.

It is a super-2 number, since 2×21902015² = 959396522120450, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2190197 + ... + 2190206.

It is an arithmetic number, because the mean of its divisors is an integer number (6570606).

Almost surely, 2^21902015 is an apocalyptic number.

21902015 is a deficient number, since it is larger than the sum of its proper divisors (4380409).

21902015 is an equidigital number, since it uses as much as digits as its factorization.

21902015 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4380408.

The product of its (nonzero) digits is 180, while the sum is 20.

The square root of 21902015 is about 4679.9588673406. The cubic root of 21902015 is about 279.7873172325.

Adding to 21902015 its reverse (51020912), we get a palindrome (72922927).

The spelling of 21902015 in words is "twenty-one million, nine hundred two thousand, fifteen".