21913615 has 4 divisors (see below), whose sum is σ = 26296344. Its totient is φ = 17530888.

The previous prime is 21913601. The next prime is 21913627. The reversal of 21913615 is 51631912.

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 21913615 - 2¹⁵ = 21880847 is a prime.

It is a Duffinian number.

It is a congruent number.

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 3 ways as a sum of consecutive naturals, for example, 2191357 + ... + 2191366.

It is an arithmetic number, because the mean of its divisors is an integer number (6574086).

Almost surely, 2^21913615 is an apocalyptic number.

21913615 is a deficient number, since it is larger than the sum of its proper divisors (4382729).

21913615 is an equidigital number, since it uses as much as digits as its factorization.

21913615 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4382728.

The product of its digits is 1620, while the sum is 28.

The square root of 21913615 is about 4681.1980304191. The cubic root of 21913615 is about 279.8367032528.

It can be divided in two parts, 21 and 913615, that multiplied together give a triangular number (19185915 = T₆₁₉₄).

The spelling of 21913615 in words is "twenty-one million, nine hundred thirteen thousand, six hundred fifteen".