21523761 has 12 divisors (see below), whose sum is σ = 35531392. Its totient is φ = 12299256.

The previous prime is 21523753. The next prime is 21523763. The reversal of 21523761 is 16732512.

It is a happy number.

It is not a de Polignac number, because 21523761 - 2³ = 21523753 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21523763) 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 11 ways as a sum of consecutive naturals, for example, 170761 + ... + 170886.

Almost surely, 2^21523761 is an apocalyptic number.

21523761 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21523761 is a deficient number, since it is larger than the sum of its proper divisors (14007631).

21523761 is a wasteful number, since it uses less digits than its factorization.

21523761 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 341660 (or 341657 counting only the distinct ones).

The product of its digits is 2520, while the sum is 27.

The square root of 21523761 is about 4639.3707547468. The cubic root of 21523761 is about 278.1672862692.

The spelling of 21523761 in words is "twenty-one million, five hundred twenty-three thousand, seven hundred sixty-one".