21615967 has 4 divisors (see below), whose sum is σ = 21635280. Its totient is φ = 21596656.

The previous prime is 21615961. The next prime is 21615973. The reversal of 21615967 is 76951612.

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 (21615961) and next prime (21615973).

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21615967 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 (21615961) 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, 7867 + ... + 10252.

It is an arithmetic number, because the mean of its divisors is an integer number (5408820).

Almost surely, 2^21615967 is an apocalyptic number.

21615967 is a deficient number, since it is larger than the sum of its proper divisors (19313).

21615967 is a wasteful number, since it uses less digits than its factorization.

21615967 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19312.

The product of its digits is 22680, while the sum is 37.

The square root of 21615967 is about 4649.2974738126. The cubic root of 21615967 is about 278.5639355675.

It can be divided in two parts, 2161 and 5967, that added together give a triangular number (8128 = T₁₂₇).

The spelling of 21615967 in words is "twenty-one million, six hundred fifteen thousand, nine hundred sixty-seven".