81761601616 has 10 divisors (see below), whose sum is σ = 158413103162. Its totient is φ = 40880800800.

The previous prime is 81761601611. The next prime is 81761601619. The reversal of 81761601616 is 61610616718.

It can be written as a sum of positive squares in only one way, i.e., 78402240016 + 3359361600 = 280004^2 + 57960^2 .

It is a super-2 number, since 2×81761601616² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81761601611) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2555050035 + ... + 2555050066.

Almost surely, 2^81761601616 is an apocalyptic number.

It is an amenable number.

81761601616 is a deficient number, since it is larger than the sum of its proper divisors (76651501546).

81761601616 is a wasteful number, since it uses less digits than its factorization.

81761601616 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5110100109 (or 5110100103 counting only the distinct ones).

The product of its (nonzero) digits is 72576, while the sum is 43.

The spelling of 81761601616 in words is "eighty-one billion, seven hundred sixty-one million, six hundred one thousand, six hundred sixteen".