21869839 has 2 divisors, whose sum is σ = 21869840. Its totient is φ = 21869838.

The previous prime is 21869821. The next prime is 21869879. The reversal of 21869839 is 93896812.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21869839 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21869879) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10934919 + 10934920.

It is an arithmetic number, because the mean of its divisors is an integer number (10934920).

Almost surely, 2^21869839 is an apocalyptic number.

21869839 is a deficient number, since it is larger than the sum of its proper divisors (1).

21869839 is an equidigital number, since it uses as much as digits as its factorization.

21869839 is an evil number, because the sum of its binary digits is even.

The product of its digits is 186624, while the sum is 46.

The square root of 21869839 is about 4676.5199668129. The cubic root of 21869839 is about 279.6502393004.

The spelling of 21869839 in words is "twenty-one million, eight hundred sixty-nine thousand, eight hundred thirty-nine".