21636394 has 12 divisors (see below), whose sum is σ = 35143686. Its totient is φ = 9985872.

The previous prime is 21636389. The next prime is 21636401. The reversal of 21636394 is 49363612.

It is a happy number.

It can be written as a sum of positive squares in 3 ways, for example, as 18378369 + 3258025 = 4287^2 + 1805^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 31669 + ... + 32344.

Almost surely, 2^21636394 is an apocalyptic number.

21636394 is a deficient number, since it is larger than the sum of its proper divisors (13507292).

21636394 is a wasteful number, since it uses less digits than its factorization.

21636394 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 64041 (or 64028 counting only the distinct ones).

The product of its digits is 23328, while the sum is 34.

The square root of 21636394 is about 4651.4937385747. The cubic root of 21636394 is about 278.6516552000.

The spelling of 21636394 in words is "twenty-one million, six hundred thirty-six thousand, three hundred ninety-four".