81859551 has 4 divisors (see below), whose sum is σ = 109146072. Its totient is φ = 54573032.

The previous prime is 81859549. The next prime is 81859579. The reversal of 81859551 is 15595818.

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 81859551 - 2¹ = 81859549 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81859511) 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, 13643256 + ... + 13643261.

It is an arithmetic number, because the mean of its divisors is an integer number (27286518).

Almost surely, 2^81859551 is an apocalyptic number.

81859551 is a deficient number, since it is larger than the sum of its proper divisors (27286521).

81859551 is a wasteful number, since it uses less digits than its factorization.

81859551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27286520.

The product of its digits is 72000, while the sum is 42.

The square root of 81859551 is about 9047.6268159115. The cubic root of 81859551 is about 434.1999669583.

The spelling of 81859551 in words is "eighty-one million, eight hundred fifty-nine thousand, five hundred fifty-one".