21615404 has 6 divisors (see below), whose sum is σ = 37826964. Its totient is φ = 10807700.

The previous prime is 21615379. The next prime is 21615409. The reversal of 21615404 is 40451612.

It is a self number, because there is not a number n which added to its sum of digits gives 21615404.

It is not an unprimeable number, because it can be changed into a prime (21615409) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2701922 + ... + 2701929.

It is an arithmetic number, because the mean of its divisors is an integer number (6304494).

Almost surely, 2^21615404 is an apocalyptic number.

It is an amenable number.

21615404 is a deficient number, since it is larger than the sum of its proper divisors (16211560).

21615404 is a wasteful number, since it uses less digits than its factorization.

21615404 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5403855 (or 5403853 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 23.

The square root of 21615404 is about 4649.2369266365. The cubic root of 21615404 is about 278.5615170952.

The spelling of 21615404 in words is "twenty-one million, six hundred fifteen thousand, four hundred four".