21085540 has 24 divisors (see below), whose sum is σ = 50605632. Its totient is φ = 7229280.

The previous prime is 21085531. The next prime is 21085541. The reversal of 21085540 is 4558012.

It is not an unprimeable number, because it can be changed into a prime (21085541) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 75166 + ... + 75445.

It is an arithmetic number, because the mean of its divisors is an integer number (2108568).

Almost surely, 2^21085540 is an apocalyptic number.

21085540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21085540 is an abundant number, since it is smaller than the sum of its proper divisors (29520092).

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

21085540 is a wasteful number, since it uses less digits than its factorization.

21085540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 150627 (or 150625 counting only the distinct ones).

The product of its (nonzero) digits is 1600, while the sum is 25.

The square root of 21085540 is about 4591.8993891417. The cubic root of 21085540 is about 276.2665107554.

The spelling of 21085540 in words is "twenty-one million, eighty-five thousand, five hundred forty".