21210744 has 16 divisors (see below), whose sum is σ = 53026920. Its totient is φ = 7070240.

The previous prime is 21210743. The next prime is 21210767. The reversal of 21210744 is 44701212.

It is a happy number.

It is a super-2 number, since 2×21210744² = 899791322067072, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21210744.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21210743) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 441867 + ... + 441914.

Almost surely, 2^21210744 is an apocalyptic number.

21210744 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21210744 is an abundant number, since it is smaller than the sum of its proper divisors (31816176).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21210744 is a wasteful number, since it uses less digits than its factorization.

21210744 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 883790 (or 883786 counting only the distinct ones).

The product of its (nonzero) digits is 448, while the sum is 21.

The square root of 21210744 is about 4605.5123493483. The cubic root of 21210744 is about 276.8122470552.

Adding to 21210744 its reverse (44701212), we get a palindrome (65911956).

The spelling of 21210744 in words is "twenty-one million, two hundred ten thousand, seven hundred forty-four".