21839720 has 32 divisors (see below), whose sum is σ = 56160000. Its totient is φ = 7487808.

The previous prime is 21839689. The next prime is 21839723. The reversal of 21839720 is 2793812.

It is not an unprimeable number, because it can be changed into a prime (21839723) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 38720 + ... + 39279.

It is an arithmetic number, because the mean of its divisors is an integer number (1755000).

Almost surely, 2^21839720 is an apocalyptic number.

21839720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21839720 is an abundant number, since it is smaller than the sum of its proper divisors (34320280).

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

21839720 is a wasteful number, since it uses less digits than its factorization.

21839720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 78017 (or 78013 counting only the distinct ones).

The product of its (nonzero) digits is 6048, while the sum is 32.

The square root of 21839720 is about 4673.2986208887. The cubic root of 21839720 is about 279.5218028249.

The spelling of 21839720 in words is "twenty-one million, eight hundred thirty-nine thousand, seven hundred twenty".