21155520 has 56 divisors (see below), whose sum is σ = 67171824. Its totient is φ = 5641216.

The previous prime is 21155513. The next prime is 21155543. The reversal of 21155520 is 2555112.

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, 10059 + ... + 11978.

Almost surely, 2^21155520 is an apocalyptic number.

21155520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21155520 is an abundant number, since it is smaller than the sum of its proper divisors (46016304).

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

21155520 is a wasteful number, since it uses less digits than its factorization.

21155520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22057 (or 22047 counting only the distinct ones).

The product of its (nonzero) digits is 500, while the sum is 21.

The square root of 21155520 is about 4599.5130177009. The cubic root of 21155520 is about 276.5718034152.

It can be divided in two parts, 211555 and 20, that added together give a triangular number (211575 = T₆₅₀).

The spelling of 21155520 in words is "twenty-one million, one hundred fifty-five thousand, five hundred twenty".