21512764 has 36 divisors (see below), whose sum is σ = 47168184. Its totient is φ = 8509536.

The previous prime is 21512759. The next prime is 21512767. The reversal of 21512764 is 46721512.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21512767) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1674 + ... + 6769.

Almost surely, 2^21512764 is an apocalyptic number.

It is an amenable number.

21512764 is an abundant number, since it is smaller than the sum of its proper divisors (25655420).

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

21512764 is a wasteful number, since it uses less digits than its factorization.

21512764 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8474 (or 8465 counting only the distinct ones).

The product of its digits is 3360, while the sum is 28.

The square root of 21512764 is about 4638.1854210456. The cubic root of 21512764 is about 278.1199041106.

It can be divided in two parts, 215127 and 64, that multiplied together give a triangular number (13768128 = T₅₂₄₇).

The spelling of 21512764 in words is "twenty-one million, five hundred twelve thousand, seven hundred sixty-four".