81551623 has 4 divisors (see below), whose sum is σ = 81610200. Its totient is φ = 81493048.

The previous prime is 81551581. The next prime is 81551633. The reversal of 81551623 is 32615518.

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 81551623 - 2²¹ = 79454471 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 (81551633) 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, 27148 + ... + 30001.

It is an arithmetic number, because the mean of its divisors is an integer number (20402550).

Almost surely, 2^81551623 is an apocalyptic number.

81551623 is a deficient number, since it is larger than the sum of its proper divisors (58577).

81551623 is a wasteful number, since it uses less digits than its factorization.

81551623 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 58576.

The product of its digits is 7200, while the sum is 31.

The square root of 81551623 is about 9030.5937235599. The cubic root of 81551623 is about 433.6548449589.

The spelling of 81551623 in words is "eighty-one million, five hundred fifty-one thousand, six hundred twenty-three".