21213736 has 8 divisors (see below), whose sum is σ = 39775770. Its totient is φ = 10606864.

The previous prime is 21213719. The next prime is 21213781. The reversal of 21213736 is 63731212.

It can be written as a sum of positive squares in only one way, i.e., 21104836 + 108900 = 4594^2 + 330^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a self number, because there is not a number n which added to its sum of digits gives 21213736.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1325851 + ... + 1325866.

Almost surely, 2^21213736 is an apocalyptic number.

It is an amenable number.

21213736 is a deficient number, since it is larger than the sum of its proper divisors (18562034).

21213736 is a wasteful number, since it uses less digits than its factorization.

21213736 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2651723 (or 2651719 counting only the distinct ones).

The product of its digits is 1512, while the sum is 25.

The square root of 21213736 is about 4605.8371660318. The cubic root of 21213736 is about 276.8252622093.

Adding to 21213736 its reverse (63731212), we get a palindrome (84944948).

The spelling of 21213736 in words is "twenty-one million, two hundred thirteen thousand, seven hundred thirty-six".