21987308 has 48 divisors (see below), whose sum is σ = 46147584. Its totient is φ = 8968320.

The previous prime is 21987299. The next prime is 21987331. The reversal of 21987308 is 80378912.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 63191 + ... + 63537.

It is an arithmetic number, because the mean of its divisors is an integer number (961408).

Almost surely, 2^21987308 is an apocalyptic number.

21987308 is a gapful number since it is divisible by the number (28) 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 21987308, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23073792).

21987308 is an abundant number, since it is smaller than the sum of its proper divisors (24160276).

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

21987308 is a wasteful number, since it uses less digits than its factorization.

21987308 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 462 (or 460 counting only the distinct ones).

The product of its (nonzero) digits is 24192, while the sum is 38.

The square root of 21987308 is about 4689.0625928857. The cubic root of 21987308 is about 280.1500386347.

The spelling of 21987308 in words is "twenty-one million, nine hundred eighty-seven thousand, three hundred eight".