21147397917 has 8 divisors (see below), whose sum is σ = 29680558560. Its totient is φ = 13356251280.

The previous prime is 21147397897. The next prime is 21147397919. The reversal of 21147397917 is 71979374112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21147397917 - 2²⁶ = 21080289053 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21147397917.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21147397919) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 185503434 + ... + 185503547.

It is an arithmetic number, because the mean of its divisors is an integer number (3710069820).

Almost surely, 2^21147397917 is an apocalyptic number.

It is an amenable number.

21147397917 is a deficient number, since it is larger than the sum of its proper divisors (8533160643).

21147397917 is a wasteful number, since it uses less digits than its factorization.

21147397917 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 371007003.

The product of its digits is 666792, while the sum is 51.

The spelling of 21147397917 in words is "twenty-one billion, one hundred forty-seven million, three hundred ninety-seven thousand, nine hundred seventeen".