21157080 has 128 divisors (see below), whose sum is σ = 73612800. Its totient is φ = 4764672.

The previous prime is 21157067. The next prime is 21157091. The reversal of 21157080 is 8075112.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 21157080.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 74619 + ... + 74901.

It is an arithmetic number, because the mean of its divisors is an integer number (575100).

Almost surely, 2^21157080 is an apocalyptic number.

21157080 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 21157080, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36806400).

21157080 is an abundant number, since it is smaller than the sum of its proper divisors (52455720).

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

21157080 is a wasteful number, since it uses less digits than its factorization.

21157080 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 393 (or 389 counting only the distinct ones).

The product of its (nonzero) digits is 560, while the sum is 24.

The square root of 21157080 is about 4599.6825977452. The cubic root of 21157080 is about 276.5786013480.

It can be divided in two parts, 211 and 57080, that added together give a triangular number (57291 = T₃₃₈).

The spelling of 21157080 in words is "twenty-one million, one hundred fifty-seven thousand, eighty".