21994186868491 has 2 divisors, whose sum is σ = 21994186868492. Its totient is φ = 21994186868490.

The previous prime is 21994186868477. The next prime is 21994186868531. The reversal of 21994186868491 is 19486868149912.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21994186868491 is a prime.

It is a super-2 number, since 2×21994186868491² (a number of 27 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21994186860491) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10997093434245 + 10997093434246.

It is an arithmetic number, because the mean of its divisors is an integer number (10997093434246).

Almost surely, 2^{21994186868491} is an apocalyptic number.

21994186868491 is a deficient number, since it is larger than the sum of its proper divisors (1).

21994186868491 is an equidigital number, since it uses as much as digits as its factorization.

21994186868491 is an evil number, because the sum of its binary digits is even.

The product of its digits is 429981696, while the sum is 76.

The spelling of 21994186868491 in words is "twenty-one trillion, nine hundred ninety-four billion, one hundred eighty-six million, eight hundred sixty-eight thousand, four hundred ninety-one".