81688532 has 6 divisors (see below), whose sum is σ = 142954938. Its totient is φ = 40844264.

The previous prime is 81688507. The next prime is 81688547. The reversal of 81688532 is 23588618.

It can be written as a sum of positive squares in only one way, i.e., 70492816 + 11195716 = 8396^2 + 3346^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 81688532.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10211063 + ... + 10211070.

It is an arithmetic number, because the mean of its divisors is an integer number (23825823).

Almost surely, 2^81688532 is an apocalyptic number.

It is an amenable number.

81688532 is a deficient number, since it is larger than the sum of its proper divisors (61266406).

81688532 is a wasteful number, since it uses less digits than its factorization.

81688532 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20422137 (or 20422135 counting only the distinct ones).

The product of its digits is 92160, while the sum is 41.

The square root of 81688532 is about 9038.1708326409. The cubic root of 81688532 is about 433.8973827763.

The spelling of 81688532 in words is "eighty-one million, six hundred eighty-eight thousand, five hundred thirty-two".