21357980 has 48 divisors (see below), whose sum is σ = 51522240. Its totient is φ = 7285248.

The previous prime is 21357979. The next prime is 21357983. The reversal of 21357980 is 8975312.

It is a Harshad number since it is a multiple of its sum of digits (35).

It is a self number, because there is not a number n which added to its sum of digits gives 21357980.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21357983) 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 15 ways as a sum of consecutive naturals, for example, 52016 + ... + 52424.

It is an arithmetic number, because the mean of its divisors is an integer number (1073380).

Almost surely, 2^21357980 is an apocalyptic number.

21357980 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21357980 is an abundant number, since it is smaller than the sum of its proper divisors (30164260).

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

21357980 is a wasteful number, since it uses less digits than its factorization.

21357980 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 798 (or 796 counting only the distinct ones).

The product of its (nonzero) digits is 15120, while the sum is 35.

The square root of 21357980 is about 4621.4694632768. The cubic root of 21357980 is about 277.4512751613.

The spelling of 21357980 in words is "twenty-one million, three hundred fifty-seven thousand, nine hundred eighty".