21317783861 has 16 divisors (see below), whose sum is σ = 23806986048. Its totient is φ = 18923923200.

The previous prime is 21317783849. The next prime is 21317783881. The reversal of 21317783861 is 16838771312.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21317783861 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21317783821) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 36365 + ... + 209661.

It is an arithmetic number, because the mean of its divisors is an integer number (1487936628).

Almost surely, 2^21317783861 is an apocalyptic number.

It is an amenable number.

21317783861 is a deficient number, since it is larger than the sum of its proper divisors (2489202187).

21317783861 is a wasteful number, since it uses less digits than its factorization.

21317783861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 173572.

The product of its digits is 338688, while the sum is 47.

The spelling of 21317783861 in words is "twenty-one billion, three hundred seventeen million, seven hundred eighty-three thousand, eight hundred sixty-one".