21897939 has 8 divisors (see below), whose sum is σ = 33368320. Its totient is φ = 12513096.

The previous prime is 21897913. The next prime is 21897949. The reversal of 21897939 is 93979812.

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

It is not a de Polignac number, because 21897939 - 2⁵ = 21897907 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21897949) 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, 521359 + ... + 521400.

It is an arithmetic number, because the mean of its divisors is an integer number (4171040).

Almost surely, 2^21897939 is an apocalyptic number.

21897939 is a deficient number, since it is larger than the sum of its proper divisors (11470381).

21897939 is a wasteful number, since it uses less digits than its factorization.

21897939 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1042769.

The product of its digits is 244944, while the sum is 48.

The square root of 21897939 is about 4679.5233731653. The cubic root of 21897939 is about 279.7699598668.

The spelling of 21897939 in words is "twenty-one million, eight hundred ninety-seven thousand, nine hundred thirty-nine".