81699121 has 6 divisors (see below), whose sum is σ = 95037810. Its totient is φ = 70027776.

The previous prime is 81699103. The next prime is 81699133. The reversal of 81699121 is 12199618.

It can be written as a sum of positive squares in only one way, i.e., 72931600 + 8767521 = 8540^2 + 2961^2 .

It is not a de Polignac number, because 81699121 - 2¹³ = 81690929 is a prime.

It is a super-3 number, since 3×81699121³ (a number of 25 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (81699181) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 833616 + ... + 833713.

It is an arithmetic number, because the mean of its divisors is an integer number (15839635).

Almost surely, 2^81699121 is an apocalyptic number.

It is an amenable number.

81699121 is a deficient number, since it is larger than the sum of its proper divisors (13338689).

81699121 is a wasteful number, since it uses less digits than its factorization.

81699121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1667343 (or 1667336 counting only the distinct ones).

The product of its digits is 7776, while the sum is 37.

The square root of 81699121 is about 9038.7566069676. The cubic root of 81699121 is about 433.9161301686.

The spelling of 81699121 in words is "eighty-one million, six hundred ninety-nine thousand, one hundred twenty-one".