81691910 has 8 divisors (see below), whose sum is σ = 147045456. Its totient is φ = 32676760.

The previous prime is 81691901. The next prime is 81691933. The reversal of 81691910 is 1919618.

It is a sphenic number, since it is the product of 3 distinct primes.

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, 4084586 + ... + 4084605.

It is an arithmetic number, because the mean of its divisors is an integer number (18380682).

Almost surely, 2^81691910 is an apocalyptic number.

81691910 is a deficient number, since it is larger than the sum of its proper divisors (65353546).

81691910 is a wasteful number, since it uses less digits than its factorization.

81691910 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8169198.

The product of its (nonzero) digits is 3888, while the sum is 35.

The square root of 81691910 is about 9038.3577048046. The cubic root of 81691910 is about 433.9033635634.

The spelling of 81691910 in words is "eighty-one million, six hundred ninety-one thousand, nine hundred ten".