21087980 has 24 divisors (see below), whose sum is σ = 44416512. Its totient is φ = 8410112.

The previous prime is 21087971. The next prime is 21087991. The reversal of 21087980 is 8978012.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 21087980.

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, 6284 + ... + 9036.

It is an arithmetic number, because the mean of its divisors is an integer number (1850688).

Almost surely, 2^21087980 is an apocalyptic number.

21087980 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21087980 is an abundant number, since it is smaller than the sum of its proper divisors (23328532).

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

21087980 is a wasteful number, since it uses less digits than its factorization.

21087980 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3145 (or 3143 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 35.

The square root of 21087980 is about 4592.1650667196. The cubic root of 21087980 is about 276.2771667829.

The spelling of 21087980 in words is "twenty-one million, eighty-seven thousand, nine hundred eighty".