21979789 has 32 divisors (see below), whose sum is σ = 26853120. Its totient is φ = 17791488.

The previous prime is 21979787. The next prime is 21979807. The reversal of 21979789 is 98797912.

It is not a de Polignac number, because 21979789 - 2¹ = 21979787 is a prime.

It is a super-2 number, since 2×21979789² = 966222248969042, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21979781) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 301057 + ... + 301129.

It is an arithmetic number, because the mean of its divisors is an integer number (839160).

Almost surely, 2^21979789 is an apocalyptic number.

It is an amenable number.

21979789 is a deficient number, since it is larger than the sum of its proper divisors (4873331).

21979789 is a wasteful number, since it uses less digits than its factorization.

21979789 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 181.

The product of its digits is 571536, while the sum is 52.

The square root of 21979789 is about 4688.2607649319. The cubic root of 21979789 is about 280.1181006897.

It can be divided in two parts, 219 and 79789, that added together give a palindrome (80008).

The spelling of 21979789 in words is "twenty-one million, nine hundred seventy-nine thousand, seven hundred eighty-nine".