81770681 has 4 divisors (see below), whose sum is σ = 85325952. Its totient is φ = 78215412.

The previous prime is 81770669. The next prime is 81770693. The reversal of 81770681 is 18607718.

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, and also an emirpimes, since its reverse is a distinct semiprime: 18607718 = 2 ⋅9303859.

It is an interprime number because it is at equal distance from previous prime (81770669) and next prime (81770693).

It is a cyclic number.

It is not a de Polignac number, because 81770681 - 2⁶ = 81770617 is a prime.

It is a super-2 number, since 2×81770681² = 13372888542407522, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81770641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1777601 + ... + 1777646.

It is an arithmetic number, because the mean of its divisors is an integer number (21331488).

Almost surely, 2^81770681 is an apocalyptic number.

It is an amenable number.

81770681 is a deficient number, since it is larger than the sum of its proper divisors (3555271).

81770681 is a wasteful number, since it uses less digits than its factorization.

81770681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3555270.

The product of its (nonzero) digits is 18816, while the sum is 38.

The square root of 81770681 is about 9042.7142496045. The cubic root of 81770681 is about 434.0427817836.

The spelling of 81770681 in words is "eighty-one million, seven hundred seventy thousand, six hundred eighty-one".