21985540 has 24 divisors (see below), whose sum is σ = 46271232. Its totient is φ = 8774880.

The previous prime is 21985531. The next prime is 21985549. The reversal of 21985540 is 4558912.

It is an interprime number because it is at equal distance from previous prime (21985531) and next prime (21985549).

It is a junction number, because it is equal to n+sod(n) for n = 21985496 and 21985505.

It is not an unprimeable number, because it can be changed into a prime (21985549) 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, 11235 + ... + 13045.

It is an arithmetic number, because the mean of its divisors is an integer number (1927968).

Almost surely, 2^21985540 is an apocalyptic number.

21985540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21985540 is an abundant number, since it is smaller than the sum of its proper divisors (24285692).

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

21985540 is a wasteful number, since it uses less digits than its factorization.

21985540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2427 (or 2425 counting only the distinct ones).

The product of its (nonzero) digits is 14400, while the sum is 34.

The square root of 21985540 is about 4688.8740652741. The cubic root of 21985540 is about 280.1425294762.

The spelling of 21985540 in words is "twenty-one million, nine hundred eighty-five thousand, five hundred forty".