21506763 has 4 divisors (see below), whose sum is σ = 28675688. Its totient is φ = 14337840.

The previous prime is 21506753. The next prime is 21506843. The reversal of 21506763 is 36760512.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21506763 - 2²⁴ = 4729547 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21506763.

It is not an unprimeable number, because it can be changed into a prime (21506753) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3584458 + ... + 3584463.

It is an arithmetic number, because the mean of its divisors is an integer number (7168922).

Almost surely, 2^21506763 is an apocalyptic number.

21506763 is a deficient number, since it is larger than the sum of its proper divisors (7168925).

21506763 is an equidigital number, since it uses as much as digits as its factorization.

21506763 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7168924.

The product of its (nonzero) digits is 7560, while the sum is 30.

The square root of 21506763 is about 4637.5384634524. The cubic root of 21506763 is about 278.0940411275.

The spelling of 21506763 in words is "twenty-one million, five hundred six thousand, seven hundred sixty-three".