21561860 has 24 divisors (see below), whose sum is σ = 45372096. Its totient is φ = 8607200.

The previous prime is 21561851. The next prime is 21561887. The reversal of 21561860 is 6816512.

It is a happy number.

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, 14135 + ... + 15585.

It is an arithmetic number, because the mean of its divisors is an integer number (1890504).

Almost surely, 2^21561860 is an apocalyptic number.

21561860 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21561860 is an abundant number, since it is smaller than the sum of its proper divisors (23810236).

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

21561860 is a wasteful number, since it uses less digits than its factorization.

21561860 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2203 (or 2201 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 29.

The square root of 21561860 is about 4643.4749918569. The cubic root of 21561860 is about 278.3313165937.

The spelling of 21561860 in words is "twenty-one million, five hundred sixty-one thousand, eight hundred sixty".