21523780 has 24 divisors (see below), whose sum is σ = 45366552. Its totient is φ = 8577792.

The previous prime is 21523769. The next prime is 21523793. The reversal of 21523780 is 8732512.

It can be written as a sum of positive squares in 4 ways, for example, as 2304324 + 19219456 = 1518^2 + 4384^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4024 + ... + 7696.

It is an arithmetic number, because the mean of its divisors is an integer number (1890273).

Almost surely, 2^21523780 is an apocalyptic number.

21523780 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21523780 is an abundant number, since it is smaller than the sum of its proper divisors (23842772).

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

21523780 is a wasteful number, since it uses less digits than its factorization.

21523780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3975 (or 3973 counting only the distinct ones).

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

The square root of 21523780 is about 4639.3728024378. The cubic root of 21523780 is about 278.1673681195.

The spelling of 21523780 in words is "twenty-one million, five hundred twenty-three thousand, seven hundred eighty".