81051781 has 16 divisors (see below), whose sum is σ = 86169600. Its totient is φ = 76120128.

The previous prime is 81051743. The next prime is 81051791. The reversal of 81051781 is 18715018.

It is not a de Polignac number, because 81051781 - 2⁷ = 81051653 is a prime.

It is a super-2 number, since 2×81051781² = 13138782406543922, 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 (81051731) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 217111 + ... + 217483.

It is an arithmetic number, because the mean of its divisors is an integer number (5385600).

Almost surely, 2^81051781 is an apocalyptic number.

It is an amenable number.

81051781 is a deficient number, since it is larger than the sum of its proper divisors (5117819).

81051781 is a wasteful number, since it uses less digits than its factorization.

81051781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 588.

The product of its (nonzero) digits is 2240, while the sum is 31.

The square root of 81051781 is about 9002.8762626174. The cubic root of 81051781 is about 432.7670503722.

Adding to 81051781 its reverse (18715018), we get a palindrome (99766799).

The spelling of 81051781 in words is "eighty-one million, fifty-one thousand, seven hundred eighty-one".