81640642 has 8 divisors (see below), whose sum is σ = 122504256. Its totient is φ = 40805892.

The previous prime is 81640627. The next prime is 81640649. The reversal of 81640642 is 24604618.

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

It is not an unprimeable number, because it can be changed into a prime (81640649) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2443 + ... + 13009.

It is an arithmetic number, because the mean of its divisors is an integer number (15313032).

Almost surely, 2^81640642 is an apocalyptic number.

81640642 is a deficient number, since it is larger than the sum of its proper divisors (40863614).

81640642 is a wasteful number, since it uses less digits than its factorization.

81640642 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14432.

The product of its (nonzero) digits is 9216, while the sum is 31.

The square root of 81640642 is about 9035.5211249822. The cubic root of 81640642 is about 433.8125752474.

The spelling of 81640642 in words is "eighty-one million, six hundred forty thousand, six hundred forty-two".