21157120 has 36 divisors (see below), whose sum is σ = 50680980. Its totient is φ = 8462336.

The previous prime is 21157117. The next prime is 21157121. The reversal of 21157120 is 2175112.

It can be written as a sum of positive squares in 2 ways, for example, as 14017536 + 7139584 = 3744^2 + 2672^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21157121) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6985 + ... + 9544.

It is an arithmetic number, because the mean of its divisors is an integer number (1407805).

Almost surely, 2^21157120 is an apocalyptic number.

21157120 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21157120 is an abundant number, since it is smaller than the sum of its proper divisors (29523860).

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

21157120 is an equidigital number, since it uses as much as digits as its factorization.

21157120 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16550 (or 16536 counting only the distinct ones).

The product of its (nonzero) digits is 140, while the sum is 19.

The square root of 21157120 is about 4599.6869458693. The cubic root of 21157120 is about 276.5787756496.

The spelling of 21157120 in words is "twenty-one million, one hundred fifty-seven thousand, one hundred twenty".