21519918 has 60 divisors (see below), whose sum is σ = 56113992. Its totient is φ = 6146280.

The previous prime is 21519907. The next prime is 21519919. The reversal of 21519918 is 81991512.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21519919) by changing a digit.

It is a polite number, since it can be written in 29 ways as a sum of consecutive naturals, for example, 6583 + ... + 9293.

Almost surely, 2^21519918 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21519918, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28056996).

21519918 is an abundant number, since it is smaller than the sum of its proper divisors (34594074).

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

21519918 is a wasteful number, since it uses less digits than its factorization.

21519918 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2739 (or 2723 counting only the distinct ones).

The product of its digits is 6480, while the sum is 36.

The square root of 21519918 is about 4638.9565637113. The cubic root of 21519918 is about 278.1507299850.

The spelling of 21519918 in words is "twenty-one million, five hundred nineteen thousand, nine hundred eighteen".