81937881 has 6 divisors (see below), whose sum is σ = 118354730. Its totient is φ = 54625248.

The previous prime is 81937879. The next prime is 81937883. The reversal of 81937881 is 18873918.

It is an interprime number because it is at equal distance from previous prime (81937879) and next prime (81937883).

It can be written as a sum of positive squares in only one way, i.e., 47610000 + 34327881 = 6900^2 + 5859^2 .

It is not a de Polignac number, because 81937881 - 2¹ = 81937879 is a prime.

It is a super-2 number, since 2×81937881² = 13427632685540322, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81937883) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 4552096 + ... + 4552113.

Almost surely, 2^81937881 is an apocalyptic number.

It is an amenable number.

81937881 is a deficient number, since it is larger than the sum of its proper divisors (36416849).

81937881 is a wasteful number, since it uses less digits than its factorization.

81937881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9104215 (or 9104212 counting only the distinct ones).

The product of its digits is 96768, while the sum is 45.

The square root of 81937881 is about 9051.9545403189. The cubic root of 81937881 is about 434.3384156411.

The spelling of 81937881 in words is "eighty-one million, nine hundred thirty-seven thousand, eight hundred eighty-one".