81951761285 has 4 divisors (see below), whose sum is σ = 98342113548. Its totient is φ = 65561409024.

The previous prime is 81951761257. The next prime is 81951761341. The reversal of 81951761285 is 58216715918.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 48330504964 + 33621256321 = 219842^2 + 183361^2 .

It is a cyclic number.

It is not a de Polignac number, because 81951761285 - 2¹² = 81951757189 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8195176124 + ... + 8195176133.

It is an arithmetic number, because the mean of its divisors is an integer number (24585528387).

Almost surely, 2^81951761285 is an apocalyptic number.

It is an amenable number.

81951761285 is a deficient number, since it is larger than the sum of its proper divisors (16390352263).

81951761285 is a wasteful number, since it uses less digits than its factorization.

81951761285 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16390352262.

The product of its digits is 1209600, while the sum is 53.

The spelling of 81951761285 in words is "eighty-one billion, nine hundred fifty-one million, seven hundred sixty-one thousand, two hundred eighty-five".