21237740 has 48 divisors (see below), whose sum is σ = 47017152. Its totient is φ = 8042496.

The previous prime is 21237739. The next prime is 21237751. The reversal of 21237740 is 4773212.

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, 62852 + ... + 63188.

It is an arithmetic number, because the mean of its divisors is an integer number (979524).

Almost surely, 2^21237740 is an apocalyptic number.

21237740 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 21237740, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23508576).

21237740 is an abundant number, since it is smaller than the sum of its proper divisors (25779412).

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

21237740 is a wasteful number, since it uses less digits than its factorization.

21237740 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 506 (or 504 counting only the distinct ones).

The product of its (nonzero) digits is 2352, while the sum is 26.

The square root of 21237740 is about 4608.4422530829. The cubic root of 21237740 is about 276.9296349745.

The spelling of 21237740 in words is "twenty-one million, two hundred thirty-seven thousand, seven hundred forty".