81964661 has 4 divisors (see below), whose sum is σ = 82089324. Its totient is φ = 81840000.

The previous prime is 81964607. The next prime is 81964669. The reversal of 81964661 is 16646918.

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 43151761 + 38812900 = 6569^2 + 6230^2 .

It is a cyclic number.

It is not a de Polignac number, because 81964661 - 2¹⁴ = 81948277 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81964669) 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, 61340 + ... + 62661.

It is an arithmetic number, because the mean of its divisors is an integer number (20522331).

Almost surely, 2^81964661 is an apocalyptic number.

It is an amenable number.

81964661 is a deficient number, since it is larger than the sum of its proper divisors (124663).

81964661 is a wasteful number, since it uses less digits than its factorization.

81964661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 124662.

The product of its digits is 62208, while the sum is 41.

The square root of 81964661 is about 9053.4336580106. The cubic root of 81964661 is about 434.3857291900.

The spelling of 81964661 in words is "eighty-one million, nine hundred sixty-four thousand, six hundred sixty-one".