81191901 has 8 divisors (see below), whose sum is σ = 123721024. Its totient is φ = 46395360.

The previous prime is 81191897. The next prime is 81191911. The reversal of 81191901 is 10919118.

It is a happy number.

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

It is not a de Polignac number, because 81191901 - 2² = 81191897 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81191911) by changing a digit.

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 in 7 ways as a sum of consecutive naturals, for example, 1933120 + ... + 1933161.

It is an arithmetic number, because the mean of its divisors is an integer number (15465128).

Almost surely, 2^81191901 is an apocalyptic number.

It is an amenable number.

81191901 is a deficient number, since it is larger than the sum of its proper divisors (42529123).

81191901 is a wasteful number, since it uses less digits than its factorization.

81191901 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3866291.

The product of its (nonzero) digits is 648, while the sum is 30.

The square root of 81191901 is about 9010.6548596648. The cubic root of 81191901 is about 433.0162918984.

The spelling of 81191901 in words is "eighty-one million, one hundred ninety-one thousand, nine hundred one".