21988791 has 12 divisors (see below), whose sum is σ = 34649160. Its totient is φ = 13326480.

The previous prime is 21988789. The next prime is 21988793. The reversal of 21988791 is 19788912.

It is an interprime number because it is at equal distance from previous prime (21988789) and next prime (21988793).

It is not a de Polignac number, because 21988791 - 2¹ = 21988789 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21988793) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 110956 + ... + 111153.

It is an arithmetic number, because the mean of its divisors is an integer number (2887430).

Almost surely, 2^21988791 is an apocalyptic number.

21988791 is a deficient number, since it is larger than the sum of its proper divisors (12660369).

21988791 is a wasteful number, since it uses less digits than its factorization.

21988791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 222126 (or 222123 counting only the distinct ones).

The product of its digits is 72576, while the sum is 45.

The square root of 21988791 is about 4689.2207241716. The cubic root of 21988791 is about 280.1563370133.

The spelling of 21988791 in words is "twenty-one million, nine hundred eighty-eight thousand, seven hundred ninety-one".