16261945681 has 2 divisors, whose sum is σ = 16261945682. Its totient is φ = 16261945680.

The previous prime is 16261945643. The next prime is 16261945723. The reversal of 16261945681 is 18654916261.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14107500625 + 2154445056 = 118775^2 + 46416^2 .

It is a cyclic number.

It is not a de Polignac number, because 16261945681 - 2²¹ = 16259848529 is a prime.

It is a super-2 number, since 2×16261945681² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (16261945081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8130972840 + 8130972841.

It is an arithmetic number, because the mean of its divisors is an integer number (8130972841).

Almost surely, 2^16261945681 is an apocalyptic number.

It is an amenable number.

16261945681 is a deficient number, since it is larger than the sum of its proper divisors (1).

16261945681 is an equidigital number, since it uses as much as digits as its factorization.

16261945681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 622080, while the sum is 49.

The spelling of 16261945681 in words is "sixteen billion, two hundred sixty-one million, nine hundred forty-five thousand, six hundred eighty-one".