81431651 has 4 divisors (see below), whose sum is σ = 93064752. Its totient is φ = 69798552.

The previous prime is 81431639. The next prime is 81431653. The reversal of 81431651 is 15613418.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 15613418 = 2 ⋅7806709.

It is a cyclic number.

It is not a de Polignac number, because 81431651 - 2²⁶ = 14322787 is a prime.

It is a super-2 number, since 2×81431651² = 13262227569171602, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81431653) 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, 5816540 + ... + 5816553.

It is an arithmetic number, because the mean of its divisors is an integer number (23266188).

Almost surely, 2^81431651 is an apocalyptic number.

81431651 is a deficient number, since it is larger than the sum of its proper divisors (11633101).

81431651 is a wasteful number, since it uses less digits than its factorization.

81431651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11633100.

The product of its digits is 2880, while the sum is 29.

The square root of 81431651 is about 9023.9487476381. The cubic root of 81431651 is about 433.4420882193.

The spelling of 81431651 in words is "eighty-one million, four hundred thirty-one thousand, six hundred fifty-one".