81909201 has 8 divisors (see below), whose sum is σ = 119140704. Its totient is φ = 49641920.

The previous prime is 81909193. The next prime is 81909227. The reversal of 81909201 is 10290918.

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

It is a cyclic number.

It is not a de Polignac number, because 81909201 - 2³ = 81909193 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81909271) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1241016 + ... + 1241081.

It is an arithmetic number, because the mean of its divisors is an integer number (14892588).

Almost surely, 2^81909201 is an apocalyptic number.

It is an amenable number.

81909201 is a deficient number, since it is larger than the sum of its proper divisors (37231503).

81909201 is a wasteful number, since it uses less digits than its factorization.

81909201 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2482111.

The product of its (nonzero) digits is 1296, while the sum is 30.

The square root of 81909201 is about 9050.3702134222. The cubic root of 81909201 is about 434.2877338349.

It can be divided in two parts, 8190 and 9201, that added together give a triangular number (17391 = T₁₈₆).

The spelling of 81909201 in words is "eighty-one million, nine hundred nine thousand, two hundred one".