21998739 has 8 divisors (see below), whose sum is σ = 33521920. Its totient is φ = 12570696.

The previous prime is 21998723. The next prime is 21998749. The reversal of 21998739 is 93789912.

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

It is not a de Polignac number, because 21998739 - 2⁴ = 21998723 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21998749) 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, 523759 + ... + 523800.

It is an arithmetic number, because the mean of its divisors is an integer number (4190240).

Almost surely, 2^21998739 is an apocalyptic number.

21998739 is a deficient number, since it is larger than the sum of its proper divisors (11523181).

21998739 is a wasteful number, since it uses less digits than its factorization.

21998739 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1047569.

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

The square root of 21998739 is about 4690.2813348455. The cubic root of 21998739 is about 280.1985793699.

The spelling of 21998739 in words is "twenty-one million, nine hundred ninety-eight thousand, seven hundred thirty-nine".