21540870 has 192 divisors, whose sum is σ = 69128640. Its totient is φ = 4727808.

The previous prime is 21540863. The next prime is 21540901. The reversal of 21540870 is 7804512.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 1133721 + ... + 1133739.

It is an arithmetic number, because the mean of its divisors is an integer number (360045).

Almost surely, 2^21540870 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21540870, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34564320).

21540870 is an abundant number, since it is smaller than the sum of its proper divisors (47587770).

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

21540870 is a wasteful number, since it uses less digits than its factorization.

21540870 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 84 (or 59 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 27.

The square root of 21540870 is about 4641.2142807675. The cubic root of 21540870 is about 278.2409707839.

The spelling of 21540870 in words is "twenty-one million, five hundred forty thousand, eight hundred seventy".