21547980 has 72 divisors (see below), whose sum is σ = 66502800. Its totient is φ = 5645952.

The previous prime is 21547979. The next prime is 21547991. The reversal of 21547980 is 8974512.

21547980 is a `hidden beast` number, since 21 + 547 + 98 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 9606 + ... + 11634.

It is an arithmetic number, because the mean of its divisors is an integer number (923650).

Almost surely, 2^21547980 is an apocalyptic number.

21547980 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21547980, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33251400).

21547980 is an abundant number, since it is smaller than the sum of its proper divisors (44954820).

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

21547980 is a wasteful number, since it uses less digits than its factorization.

21547980 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2103 (or 2098 counting only the distinct ones).

The product of its (nonzero) digits is 20160, while the sum is 36.

The square root of 21547980 is about 4641.9801809142. The cubic root of 21547980 is about 278.2715804372.

The spelling of 21547980 in words is "twenty-one million, five hundred forty-seven thousand, nine hundred eighty".