21761423681 has 2 divisors, whose sum is σ = 21761423682. Its totient is φ = 21761423680.

The previous prime is 21761423669. The next prime is 21761423713. The reversal of 21761423681 is 18632416712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12191693056 + 9569730625 = 110416^2 + 97825^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21761423681 is a prime.

It is a super-2 number, since 2×21761423681² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21761426681) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10880711840 + 10880711841.

It is an arithmetic number, because the mean of its divisors is an integer number (10880711841).

Almost surely, 2^21761423681 is an apocalyptic number.

It is an amenable number.

21761423681 is a deficient number, since it is larger than the sum of its proper divisors (1).

21761423681 is an equidigital number, since it uses as much as digits as its factorization.

21761423681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 96768, while the sum is 41.

The spelling of 21761423681 in words is "twenty-one billion, seven hundred sixty-one million, four hundred twenty-three thousand, six hundred eighty-one".