21251236 has 6 divisors (see below), whose sum is σ = 37189670. Its totient is φ = 10625616.

The previous prime is 21251201. The next prime is 21251239. The reversal of 21251236 is 63215212.

It can be written as a sum of positive squares in only one way, i.e., 20430400 + 820836 = 4520^2 + 906^2 .

It is not an unprimeable number, because it can be changed into a prime (21251239) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2656401 + ... + 2656408.

Almost surely, 2^21251236 is an apocalyptic number.

It is an amenable number.

21251236 is a deficient number, since it is larger than the sum of its proper divisors (15938434).

21251236 is a wasteful number, since it uses less digits than its factorization.

21251236 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5312813 (or 5312811 counting only the distinct ones).

The product of its digits is 720, while the sum is 22.

The square root of 21251236 is about 4609.9062897200. The cubic root of 21251236 is about 276.9882829435.

Adding to 21251236 its reverse (63215212), we get a palindrome (84466448).

The spelling of 21251236 in words is "twenty-one million, two hundred fifty-one thousand, two hundred thirty-six".