81557351 has 4 divisors (see below), whose sum is σ = 81767400. Its totient is φ = 81347304.

The previous prime is 81557339. The next prime is 81557363. The reversal of 81557351 is 15375518.

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

It is an interprime number because it is at equal distance from previous prime (81557339) and next prime (81557363).

It is a cyclic number.

It is not a de Polignac number, because 81557351 - 2²² = 77363047 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81557321) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 104441 + ... + 105218.

It is an arithmetic number, because the mean of its divisors is an integer number (20441850).

Almost surely, 2^81557351 is an apocalyptic number.

81557351 is a deficient number, since it is larger than the sum of its proper divisors (210049).

81557351 is a wasteful number, since it uses less digits than its factorization.

81557351 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 210048.

The product of its digits is 21000, while the sum is 35.

The square root of 81557351 is about 9030.9108621445. The cubic root of 81557351 is about 433.6649976970.

The spelling of 81557351 in words is "eighty-one million, five hundred fifty-seven thousand, three hundred fifty-one".