81909897 has 8 divisors (see below), whose sum is σ = 112165056. Its totient is φ = 53130672.

The previous prime is 81909887. The next prime is 81909899. The reversal of 81909897 is 79890918.

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

It is not a de Polignac number, because 81909897 - 2⁴ = 81909881 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81909899) 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, 368853 + ... + 369074.

It is an arithmetic number, because the mean of its divisors is an integer number (14020632).

Almost surely, 2^81909897 is an apocalyptic number.

It is an amenable number.

81909897 is a deficient number, since it is larger than the sum of its proper divisors (30255159).

81909897 is a wasteful number, since it uses less digits than its factorization.

81909897 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 737967.

The product of its (nonzero) digits is 326592, while the sum is 51.

The square root of 81909897 is about 9050.4086648062. The cubic root of 81909897 is about 434.2889639100.

The spelling of 81909897 in words is "eighty-one million, nine hundred nine thousand, eight hundred ninety-seven".