81900997 has 4 divisors (see below), whose sum is σ = 82887840. Its totient is φ = 80914156.

The previous prime is 81900989. The next prime is 81901003. The reversal of 81900997 is 79900918.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81900997 - 2³ = 81900989 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81900947) 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, 493297 + ... + 493462.

It is an arithmetic number, because the mean of its divisors is an integer number (20721960).

Almost surely, 2^81900997 is an apocalyptic number.

It is an amenable number.

81900997 is a deficient number, since it is larger than the sum of its proper divisors (986843).

81900997 is an equidigital number, since it uses as much as digits as its factorization.

81900997 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 986842.

The product of its (nonzero) digits is 40824, while the sum is 43.

The square root of 81900997 is about 9049.9169609450. The cubic root of 81900997 is about 434.2732339762.

The spelling of 81900997 in words is "eighty-one million, nine hundred thousand, nine hundred ninety-seven".