81691935 has 16 divisors (see below), whose sum is σ = 140761824. Its totient is φ = 40217472.

The previous prime is 81691933. The next prime is 81691937. The reversal of 81691935 is 53919618.

It is an interprime number because it is at equal distance from previous prime (81691933) and next prime (81691937).

It is not a de Polignac number, because 81691935 - 2¹ = 81691933 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81691933) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 209272 + ... + 209661.

It is an arithmetic number, because the mean of its divisors is an integer number (8797614).

Almost surely, 2^81691935 is an apocalyptic number.

81691935 is a deficient number, since it is larger than the sum of its proper divisors (59069889).

81691935 is a wasteful number, since it uses less digits than its factorization.

81691935 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 418954.

The product of its digits is 58320, while the sum is 42.

The square root of 81691935 is about 9038.3590877991. The cubic root of 81691935 is about 433.9034078256.

The spelling of 81691935 in words is "eighty-one million, six hundred ninety-one thousand, nine hundred thirty-five".