21209372 has 12 divisors (see below), whose sum is σ = 37259376. Its totient is φ = 10563840.

The previous prime is 21209369. The next prime is 21209393. The reversal of 21209372 is 27390212.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9029 + ... + 11132.

It is an arithmetic number, because the mean of its divisors is an integer number (3104948).

Almost surely, 2^21209372 is an apocalyptic number.

It is an amenable number.

21209372 is a deficient number, since it is larger than the sum of its proper divisors (16050004).

21209372 is a wasteful number, since it uses less digits than its factorization.

21209372 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20428 (or 20426 counting only the distinct ones).

The product of its (nonzero) digits is 1512, while the sum is 26.

The square root of 21209372 is about 4605.3633949994. The cubic root of 21209372 is about 276.8062784670.

Adding to 21209372 its reverse (27390212), we get a palindrome (48599584).

The spelling of 21209372 in words is "twenty-one million, two hundred nine thousand, three hundred seventy-two".