21390904279 has 4 divisors (see below), whose sum is σ = 22649192784. Its totient is φ = 20132615776.

The previous prime is 21390904267. The next prime is 21390904289. The reversal of 21390904279 is 97240909312.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21390904279 - 2¹¹ = 21390902231 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21390904229) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 629144227 + ... + 629144260.

It is an arithmetic number, because the mean of its divisors is an integer number (5662298196).

Almost surely, 2^21390904279 is an apocalyptic number.

21390904279 is a deficient number, since it is larger than the sum of its proper divisors (1258288505).

21390904279 is a wasteful number, since it uses less digits than its factorization.

21390904279 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1258288504.

The product of its (nonzero) digits is 244944, while the sum is 46.

The spelling of 21390904279 in words is "twenty-one billion, three hundred ninety million, nine hundred four thousand, two hundred seventy-nine".