21502540 has 24 divisors (see below), whose sum is σ = 45313632. Its totient is φ = 8570880.

The previous prime is 21502531. The next prime is 21502571. The reversal of 21502540 is 4520512.

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, 4492 + ... + 7948.

It is an arithmetic number, because the mean of its divisors is an integer number (1888068).

Almost surely, 2^21502540 is an apocalyptic number.

21502540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21502540 is an abundant number, since it is smaller than the sum of its proper divisors (23811092).

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

21502540 is a wasteful number, since it uses less digits than its factorization.

21502540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3777 (or 3775 counting only the distinct ones).

The product of its (nonzero) digits is 400, while the sum is 19.

The square root of 21502540 is about 4637.0831349028. The cubic root of 21502540 is about 278.0758380471.

The spelling of 21502540 in words is "twenty-one million, five hundred two thousand, five hundred forty".