21394681915 has 4 divisors (see below), whose sum is σ = 25673618304. Its totient is φ = 17115745528.

The previous prime is 21394681873. The next prime is 21394681943. The reversal of 21394681915 is 51918649312.

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 21394681915 - 2²⁵ = 21361127483 is a prime.

It is a super-3 number, since 3×21394681915³ (a number of 32 digits) contains 333 as substring.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2139468187 + ... + 2139468196.

It is an arithmetic number, because the mean of its divisors is an integer number (6418404576).

Almost surely, 2^21394681915 is an apocalyptic number.

21394681915 is a deficient number, since it is larger than the sum of its proper divisors (4278936389).

21394681915 is an equidigital number, since it uses as much as digits as its factorization.

21394681915 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4278936388.

The product of its digits is 466560, while the sum is 49.

The spelling of 21394681915 in words is "twenty-one billion, three hundred ninety-four million, six hundred eighty-one thousand, nine hundred fifteen".