81691495 has 4 divisors (see below), whose sum is σ = 98029800. Its totient is φ = 65353192.

The previous prime is 81691487. The next prime is 81691501. The reversal of 81691495 is 59419618.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81691495 - 2³ = 81691487 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8169145 + ... + 8169154.

It is an arithmetic number, because the mean of its divisors is an integer number (24507450).

Almost surely, 2^81691495 is an apocalyptic number.

81691495 is a deficient number, since it is larger than the sum of its proper divisors (16338305).

81691495 is a wasteful number, since it uses less digits than its factorization.

81691495 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16338304.

The product of its digits is 77760, while the sum is 43.

The square root of 81691495 is about 9038.3347470649. The cubic root of 81691495 is about 433.9026288101.

The spelling of 81691495 in words is "eighty-one million, six hundred ninety-one thousand, four hundred ninety-five".