21615969 has 8 divisors (see below), whose sum is σ = 28842912. Its totient is φ = 14399840.

The previous prime is 21615961. The next prime is 21615973. The reversal of 21615969 is 96951612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21615969 - 2³ = 21615961 is a prime.

It is a super-2 number, since 2×21615969² = 934500231617922, which contains 22 as substring.

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 7 ways as a sum of consecutive naturals, for example, 5674 + ... + 8684.

It is an arithmetic number, because the mean of its divisors is an integer number (3605364).

Almost surely, 2^21615969 is an apocalyptic number.

It is an amenable number.

21615969 is a deficient number, since it is larger than the sum of its proper divisors (7226943).

21615969 is a wasteful number, since it uses less digits than its factorization.

21615969 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5407.

The product of its digits is 29160, while the sum is 39.

The square root of 21615969 is about 4649.2976888988. The cubic root of 21615969 is about 278.5639441588.

The spelling of 21615969 in words is "twenty-one million, six hundred fifteen thousand, nine hundred sixty-nine".