21988279 has 2 divisors, whose sum is σ = 21988280. Its totient is φ = 21988278.

The previous prime is 21988247. The next prime is 21988303. The reversal of 21988279 is 97288912.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21988279 - 2⁵ = 21988247 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21988229) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10994139 + 10994140.

It is an arithmetic number, because the mean of its divisors is an integer number (10994140).

Almost surely, 2^21988279 is an apocalyptic number.

21988279 is a deficient number, since it is larger than the sum of its proper divisors (1).

21988279 is an equidigital number, since it uses as much as digits as its factorization.

21988279 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 145152, while the sum is 46.

The square root of 21988279 is about 4689.1661305610. The cubic root of 21988279 is about 280.1541625545.

It can be divided in two parts, 219882 and 79, that added together give a square (219961 = 469²).

The spelling of 21988279 in words is "twenty-one million, nine hundred eighty-eight thousand, two hundred seventy-nine".