81355511 has 4 divisors (see below), whose sum is σ = 85637400. Its totient is φ = 77073624.

The previous prime is 81355493. The next prime is 81355541. The reversal of 81355511 is 11555318.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81355511 - 2¹⁰ = 81354487 is a prime.

It is a super-2 number, since 2×81355511² = 13237438340142242, 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 (81355541) 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, 2140916 + ... + 2140953.

It is an arithmetic number, because the mean of its divisors is an integer number (21409350).

Almost surely, 2^81355511 is an apocalyptic number.

81355511 is a deficient number, since it is larger than the sum of its proper divisors (4281889).

81355511 is a wasteful number, since it uses less digits than its factorization.

81355511 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4281888.

The product of its digits is 3000, while the sum is 29.

The square root of 81355511 is about 9019.7289870594. The cubic root of 81355511 is about 433.3069541470.

The spelling of 81355511 in words is "eighty-one million, three hundred fifty-five thousand, five hundred eleven".