81870511 has 4 divisors (see below), whose sum is σ = 81888624. Its totient is φ = 81852400.

The previous prime is 81870497. The next prime is 81870517. The reversal of 81870511 is 11507818.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81870511 is a prime.

It is a super-2 number, since 2×81870511² = 13405561142802242, 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 (81870517) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3966 + ... + 13396.

It is an arithmetic number, because the mean of its divisors is an integer number (20472156).

Almost surely, 2^81870511 is an apocalyptic number.

81870511 is a deficient number, since it is larger than the sum of its proper divisors (18113).

81870511 is an equidigital number, since it uses as much as digits as its factorization.

81870511 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18112.

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

The square root of 81870511 is about 9048.2324793299. The cubic root of 81870511 is about 434.2193441282.

The spelling of 81870511 in words is "eighty-one million, eight hundred seventy thousand, five hundred eleven".