81403681 has 4 divisors (see below), whose sum is σ = 82194112. Its totient is φ = 80613252.

The previous prime is 81403643. The next prime is 81403703. The reversal of 81403681 is 18630418.

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 a de Polignac number, because none of the positive numbers 2^k-81403681 is a prime.

It is a super-2 number, since 2×81403681² = 13253118560699522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81403481) 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 3 ways as a sum of consecutive naturals, for example, 395061 + ... + 395266.

It is an arithmetic number, because the mean of its divisors is an integer number (20548528).

Almost surely, 2^81403681 is an apocalyptic number.

It is an amenable number.

81403681 is a deficient number, since it is larger than the sum of its proper divisors (790431).

81403681 is a wasteful number, since it uses less digits than its factorization.

81403681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 790430.

The product of its (nonzero) digits is 4608, while the sum is 31.

The square root of 81403681 is about 9022.3988495300. The cubic root of 81403681 is about 433.3924565615.

The spelling of 81403681 in words is "eighty-one million, four hundred three thousand, six hundred eighty-one".