21522731 has 4 divisors (see below), whose sum is σ = 22788792. Its totient is φ = 20256672.

The previous prime is 21522719. The next prime is 21522737. The reversal of 21522731 is 13722512.

It is a happy number.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21522731 is a prime.

It is a super-2 number, since 2×21522731² = 926455899396722, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21522697 and 21522706.

It is not an unprimeable number, because it can be changed into a prime (21522737) 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, 633005 + ... + 633038.

It is an arithmetic number, because the mean of its divisors is an integer number (5697198).

Almost surely, 2^21522731 is an apocalyptic number.

21522731 is a deficient number, since it is larger than the sum of its proper divisors (1266061).

21522731 is a wasteful number, since it uses less digits than its factorization.

21522731 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1266060.

The product of its digits is 840, while the sum is 23.

The square root of 21522731 is about 4639.2597469855. The cubic root of 21522731 is about 278.1628490509.

The spelling of 21522731 in words is "twenty-one million, five hundred twenty-two thousand, seven hundred thirty-one".