21615730 has 32 divisors (see below), whose sum is σ = 42379200. Its totient is φ = 7906752.

The previous prime is 21615719. The next prime is 21615761. The reversal of 21615730 is 3751612.

It is a junction number, because it is equal to n+sod(n) for n = 21615695 and 21615704.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3549 + ... + 7471.

It is an arithmetic number, because the mean of its divisors is an integer number (1324350).

Almost surely, 2^21615730 is an apocalyptic number.

21615730 is a deficient number, since it is larger than the sum of its proper divisors (20763470).

21615730 is a wasteful number, since it uses less digits than its factorization.

21615730 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3978.

The product of its (nonzero) digits is 1260, while the sum is 25.

The square root of 21615730 is about 4649.2719860210. The cubic root of 21615730 is about 278.5629174946.

The spelling of 21615730 in words is "twenty-one million, six hundred fifteen thousand, seven hundred thirty".