81990127 has 4 divisors (see below), whose sum is σ = 82742440. Its totient is φ = 81237816.

The previous prime is 81990107. The next prime is 81990143. The reversal of 81990127 is 72109918.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81990127 is a prime.

It is a super-2 number, since 2×81990127² = 13444761850952258, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81990107) 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, 375993 + ... + 376210.

It is an arithmetic number, because the mean of its divisors is an integer number (20685610).

Almost surely, 2^81990127 is an apocalyptic number.

81990127 is a deficient number, since it is larger than the sum of its proper divisors (752313).

81990127 is a wasteful number, since it uses less digits than its factorization.

81990127 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 752312.

The product of its (nonzero) digits is 9072, while the sum is 37.

The square root of 81990127 is about 9054.8399764988. The cubic root of 81990127 is about 434.4307116715.

The spelling of 81990127 in words is "eighty-one million, nine hundred ninety thousand, one hundred twenty-seven".