81575551 has 4 divisors (see below), whose sum is σ = 81599400. Its totient is φ = 81551704.

The previous prime is 81575519. The next prime is 81575561. The reversal of 81575551 is 15557518.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 15557518 = 2 ⋅7778759.

It is a cyclic number.

It is not a de Polignac number, because 81575551 - 2⁵ = 81575519 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 81575551.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81575561) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5716 + ... + 13993.

It is an arithmetic number, because the mean of its divisors is an integer number (20399850).

Almost surely, 2^81575551 is an apocalyptic number.

81575551 is a deficient number, since it is larger than the sum of its proper divisors (23849).

81575551 is a wasteful number, since it uses less digits than its factorization.

81575551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23848.

The product of its digits is 35000, while the sum is 37.

The square root of 81575551 is about 9031.9184562307. The cubic root of 81575551 is about 433.6972535915.

The spelling of 81575551 in words is "eighty-one million, five hundred seventy-five thousand, five hundred fifty-one".