21513540 has 48 divisors (see below), whose sum is σ = 60463872. Its totient is φ = 5715456.

The previous prime is 21513523. The next prime is 21513559. The reversal of 21513540 is 4531512.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 21532 + ... + 22508.

It is an arithmetic number, because the mean of its divisors is an integer number (1259664).

Almost surely, 2^21513540 is an apocalyptic number.

21513540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21513540 is an abundant number, since it is smaller than the sum of its proper divisors (38950332).

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

21513540 is a wasteful number, since it uses less digits than its factorization.

21513540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1356 (or 1354 counting only the distinct ones).

The product of its (nonzero) digits is 600, while the sum is 21.

The square root of 21513540 is about 4638.2690736955. The cubic root of 21513540 is about 278.1232481479.

The spelling of 21513540 in words is "twenty-one million, five hundred thirteen thousand, five hundred forty".