21393959 has 2 divisors, whose sum is σ = 21393960. Its totient is φ = 21393958.

The previous prime is 21393949. The next prime is 21393961. The reversal of 21393959 is 95939312.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21393959 - 2¹⁶ = 21328423 is a prime.

Together with 21393961, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21393929) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10696979 + 10696980.

It is an arithmetic number, because the mean of its divisors is an integer number (10696980).

Almost surely, 2^21393959 is an apocalyptic number.

21393959 is a deficient number, since it is larger than the sum of its proper divisors (1).

21393959 is an equidigital number, since it uses as much as digits as its factorization.

21393959 is an evil number, because the sum of its binary digits is even.

The product of its digits is 65610, while the sum is 41.

The square root of 21393959 is about 4625.3604183890. The cubic root of 21393959 is about 277.6069830717.

The spelling of 21393959 in words is "twenty-one million, three hundred ninety-three thousand, nine hundred fifty-nine".