81975616 has 14 divisors (see below), whose sum is σ = 162670490. Its totient is φ = 40987776.

The previous prime is 81975613. The next prime is 81975623. The reversal of 81975616 is 61657918.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 81721600 + 254016 = 9040^2 + 504^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81975613) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 640371 + ... + 640498.

Almost surely, 2^81975616 is an apocalyptic number.

It is an amenable number.

81975616 is a deficient number, since it is larger than the sum of its proper divisors (80694874).

81975616 is a wasteful number, since it uses less digits than its factorization.

81975616 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1280881 (or 1280871 counting only the distinct ones).

The product of its digits is 90720, while the sum is 43.

The square root of 81975616 is about 9054.0386568647. The cubic root of 81975616 is about 434.4050809594.

The spelling of 81975616 in words is "eighty-one million, nine hundred seventy-five thousand, six hundred sixteen".