21551980 has 12 divisors (see below), whose sum is σ = 45259200. Its totient is φ = 8620784.

The previous prime is 21551969. The next prime is 21551983. The reversal of 21551980 is 8915512.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21551983) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 538780 + ... + 538819.

It is an arithmetic number, because the mean of its divisors is an integer number (3771600).

Almost surely, 2^21551980 is an apocalyptic number.

21551980 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21551980 is an abundant number, since it is smaller than the sum of its proper divisors (23707220).

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

21551980 is a wasteful number, since it uses less digits than its factorization.

21551980 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1077608 (or 1077606 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 31.

The square root of 21551980 is about 4642.4110115327. The cubic root of 21551980 is about 278.2887980983.

The spelling of 21551980 in words is "twenty-one million, five hundred fifty-one thousand, nine hundred eighty".