81870005 has 32 divisors (see below), whose sum is σ = 115762176. Its totient is φ = 54422784.

The previous prime is 81869981. The next prime is 81870013. The reversal of 81870005 is 50007818.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 81870005 - 2⁶ = 81869941 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81870005.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 258107 + ... + 258423.

It is an arithmetic number, because the mean of its divisors is an integer number (3617568).

Almost surely, 2^81870005 is an apocalyptic number.

It is an amenable number.

81870005 is a deficient number, since it is larger than the sum of its proper divisors (33892171).

81870005 is a wasteful number, since it uses less digits than its factorization.

81870005 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 533.

The product of its (nonzero) digits is 2240, while the sum is 29.

The square root of 81870005 is about 9048.2045180246. The cubic root of 81870005 is about 434.2184495633.

The spelling of 81870005 in words is "eighty-one million, eight hundred seventy thousand, five".