18721520 has 40 divisors (see below), whose sum is σ = 44937600. Its totient is φ = 7246080.

The previous prime is 18721511. The next prime is 18721537. The reversal of 18721520 is 2512781.

It is a tau number, because it is divible by the number of its divisors (40).

It is a super-2 number, since 2×18721520² = 700990622220800, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 18721520.

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 1295 + ... + 6254.

It is an arithmetic number, because the mean of its divisors is an integer number (1123440).

Almost surely, 2^18721520 is an apocalyptic number.

18721520 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

18721520 is an abundant number, since it is smaller than the sum of its proper divisors (26216080).

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

18721520 is a wasteful number, since it uses less digits than its factorization.

18721520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7593 (or 7587 counting only the distinct ones).

The product of its (nonzero) digits is 1120, while the sum is 26.

The square root of 18721520 is about 4326.8371820534. The cubic root of 18721520 is about 265.5300651745.

The spelling of 18721520 in words is "eighteen million, seven hundred twenty-one thousand, five hundred twenty".