81739961 has 4 divisors (see below), whose sum is σ = 86548212. Its totient is φ = 76931712.

The previous prime is 81739949. The next prime is 81739967. The reversal of 81739961 is 16993718.

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 55279225 + 26460736 = 7435^2 + 5144^2 .

It is a cyclic number.

It is not a de Polignac number, because 81739961 - 2⁶ = 81739897 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81739967) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2404100 + ... + 2404133.

It is an arithmetic number, because the mean of its divisors is an integer number (21637053).

Almost surely, 2^81739961 is an apocalyptic number.

It is an amenable number.

81739961 is a deficient number, since it is larger than the sum of its proper divisors (4808251).

81739961 is a wasteful number, since it uses less digits than its factorization.

81739961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4808250.

The product of its digits is 81648, while the sum is 44.

The square root of 81739961 is about 9041.0154849995. The cubic root of 81739961 is about 433.9884205537.

The spelling of 81739961 in words is "eighty-one million, seven hundred thirty-nine thousand, nine hundred sixty-one".