21534840 has 96 divisors (see below), whose sum is σ = 71744400. Its totient is φ = 5598720.

The previous prime is 21534839. The next prime is 21534841. The reversal of 21534840 is 4843512.

It is an interprime number because it is at equal distance from previous prime (21534839) and next prime (21534841).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21534841) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 14031 + ... + 15489.

Almost surely, 2^21534840 is an apocalyptic number.

21534840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21534840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35872200).

21534840 is an abundant number, since it is smaller than the sum of its proper divisors (50209560).

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

21534840 is a wasteful number, since it uses less digits than its factorization.

21534840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1517 (or 1510 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 27.

The square root of 21534840 is about 4640.5646208193. The cubic root of 21534840 is about 278.2150054193.

The spelling of 21534840 in words is "twenty-one million, five hundred thirty-four thousand, eight hundred forty".