21506860 has 24 divisors (see below), whose sum is σ = 47542320. Its totient is φ = 8149824.

The previous prime is 21506843. The next prime is 21506861. The reversal of 21506860 is 6860512.

It is not an unprimeable number, because it can be changed into a prime (21506861) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 27919 + ... + 28678.

It is an arithmetic number, because the mean of its divisors is an integer number (1980930).

Almost surely, 2^21506860 is an apocalyptic number.

21506860 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21506860 is an abundant number, since it is smaller than the sum of its proper divisors (26035460).

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

21506860 is a wasteful number, since it uses less digits than its factorization.

21506860 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56625 (or 56623 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 28.

The square root of 21506860 is about 4637.5489215748. The cubic root of 21506860 is about 278.0944592143.

It can be divided in two parts, 21506 and 860, that added together give a triangular number (22366 = T₂₁₁).

The spelling of 21506860 in words is "twenty-one million, five hundred six thousand, eight hundred sixty".