21718646431 has 2 divisors, whose sum is σ = 21718646432. Its totient is φ = 21718646430.

The previous prime is 21718646423. The next prime is 21718646491. The reversal of 21718646431 is 13464681712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21718646431 - 2³ = 21718646423 is a prime.

It is a super-2 number, since 2×21718646431² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21718646401) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10859323215 + 10859323216.

It is an arithmetic number, because the mean of its divisors is an integer number (10859323216).

Almost surely, 2^21718646431 is an apocalyptic number.

21718646431 is a deficient number, since it is larger than the sum of its proper divisors (1).

21718646431 is an equidigital number, since it uses as much as digits as its factorization.

21718646431 is an evil number, because the sum of its binary digits is even.

The product of its digits is 193536, while the sum is 43.

The spelling of 21718646431 in words is "twenty-one billion, seven hundred eighteen million, six hundred forty-six thousand, four hundred thirty-one".