21491297913 has 4 divisors (see below), whose sum is σ = 28655063888. Its totient is φ = 14327531940.

The previous prime is 21491297903. The next prime is 21491297941. The reversal of 21491297913 is 31979219412.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21491297913 - 2⁴ = 21491297897 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21491297903) 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, 3581882983 + ... + 3581882988.

It is an arithmetic number, because the mean of its divisors is an integer number (7163765972).

Almost surely, 2^21491297913 is an apocalyptic number.

It is an amenable number.

21491297913 is a deficient number, since it is larger than the sum of its proper divisors (7163765975).

21491297913 is an equidigital number, since it uses as much as digits as its factorization.

21491297913 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7163765974.

The product of its digits is 244944, while the sum is 48.

The spelling of 21491297913 in words is "twenty-one billion, four hundred ninety-one million, two hundred ninety-seven thousand, nine hundred thirteen".