21086240 has 96 divisors (see below), whose sum is σ = 57988224. Its totient is φ = 7096320.

The previous prime is 21086237. The next prime is 21086249. The reversal of 21086240 is 4268012.

It is not an unprimeable number, because it can be changed into a prime (21086249) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 74900 + ... + 75180.

It is an arithmetic number, because the mean of its divisors is an integer number (604044).

Almost surely, 2^21086240 is an apocalyptic number.

21086240 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 21086240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28994112).

21086240 is an abundant number, since it is smaller than the sum of its proper divisors (36901984).

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

21086240 is a wasteful number, since it uses less digits than its factorization.

21086240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 370 (or 362 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 23.

The square root of 21086240 is about 4591.9756096913. The cubic root of 21086240 is about 276.2695678965.

The spelling of 21086240 in words is "twenty-one million, eighty-six thousand, two hundred forty".