81298905 has 32 divisors (see below), whose sum is σ = 137687040. Its totient is φ = 40877760.

The previous prime is 81298897. The next prime is 81298907. The reversal of 81298905 is 50989218.

81298905 = T₁₅₀ + T₁₅₁ + ... + T₇₈₈.

It is a happy number.

It is not a de Polignac number, because 81298905 - 2³ = 81298897 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is not an unprimeable number, because it can be changed into a prime (81298907) 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 31 ways as a sum of consecutive naturals, for example, 22836 + ... + 26154.

It is an arithmetic number, because the mean of its divisors is an integer number (4302720).

Almost surely, 2^81298905 is an apocalyptic number.

It is an amenable number.

81298905 is a deficient number, since it is larger than the sum of its proper divisors (56388135).

81298905 is a wasteful number, since it uses less digits than its factorization.

81298905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3421.

The product of its (nonzero) digits is 51840, while the sum is 42.

The square root of 81298905 is about 9016.5905418844. The cubic root of 81298905 is about 433.2064345713.

The spelling of 81298905 in words is "eighty-one million, two hundred ninety-eight thousand, nine hundred five".