21715939 has 8 divisors (see below), whose sum is σ = 25225568. Its totient is φ = 18308160.

The previous prime is 21715931. The next prime is 21715951. The reversal of 21715939 is 93951712.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21715939 - 2³ = 21715931 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21715898 and 21715907.

It is not an unprimeable number, because it can be changed into a prime (21715931) 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, 25002 + ... + 25855.

It is an arithmetic number, because the mean of its divisors is an integer number (3153196).

Almost surely, 2^21715939 is an apocalyptic number.

21715939 is a deficient number, since it is larger than the sum of its proper divisors (3509629).

21715939 is an equidigital number, since it uses as much as digits as its factorization.

21715939 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50925.

The product of its digits is 17010, while the sum is 37.

The square root of 21715939 is about 4660.0363732486. The cubic root of 21715939 is about 278.9927200132.

The spelling of 21715939 in words is "twenty-one million, seven hundred fifteen thousand, nine hundred thirty-nine".