21665236 has 6 divisors (see below), whose sum is σ = 37914170. Its totient is φ = 10832616.

The previous prime is 21665227. The next prime is 21665243. The reversal of 21665236 is 63256612.

It can be written as a sum of positive squares in only one way, i.e., 15132100 + 6533136 = 3890^2 + 2556^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21665198 and 21665207.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2708151 + ... + 2708158.

Almost surely, 2^21665236 is an apocalyptic number.

It is an amenable number.

21665236 is a deficient number, since it is larger than the sum of its proper divisors (16248934).

21665236 is a wasteful number, since it uses less digits than its factorization.

21665236 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5416313 (or 5416311 counting only the distinct ones).

The product of its digits is 12960, while the sum is 31.

The square root of 21665236 is about 4654.5930004674. The cubic root of 21665236 is about 278.7754173904.

The spelling of 21665236 in words is "twenty-one million, six hundred sixty-five thousand, two hundred thirty-six".