21012756 has 12 divisors (see below), whose sum is σ = 49029792. Its totient is φ = 7004248.

The previous prime is 21012749. The next prime is 21012773. The reversal of 21012756 is 65721012.

It is a tau number, because it is divible by the number of its divisors (12).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 875520 + ... + 875543.

It is an arithmetic number, because the mean of its divisors is an integer number (4085816).

Almost surely, 2^21012756 is an apocalyptic number.

It is an amenable number.

21012756 is an abundant number, since it is smaller than the sum of its proper divisors (28017036).

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

21012756 is a wasteful number, since it uses less digits than its factorization.

21012756 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1751070 (or 1751068 counting only the distinct ones).

The product of its (nonzero) digits is 840, while the sum is 24.

The square root of 21012756 is about 4583.9672773701. The cubic root of 21012756 is about 275.9482679770.

Adding to 21012756 its reverse (65721012), we get a palindrome (86733768).

The spelling of 21012756 in words is "twenty-one million, twelve thousand, seven hundred fifty-six".