21397879 has 2 divisors, whose sum is σ = 21397880. Its totient is φ = 21397878.

The previous prime is 21397867. The next prime is 21397907. The reversal of 21397879 is 97879312.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21397879 - 2⁵ = 21397847 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21397829) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10698939 + 10698940.

It is an arithmetic number, because the mean of its divisors is an integer number (10698940).

Almost surely, 2^21397879 is an apocalyptic number.

21397879 is a deficient number, since it is larger than the sum of its proper divisors (1).

21397879 is an equidigital number, since it uses as much as digits as its factorization.

21397879 is an evil number, because the sum of its binary digits is even.

The product of its digits is 190512, while the sum is 46.

The square root of 21397879 is about 4625.7841497415. The cubic root of 21397879 is about 277.6239372801.

The spelling of 21397879 in words is "twenty-one million, three hundred ninety-seven thousand, eight hundred seventy-nine".