81555563 has 8 divisors (see below), whose sum is σ = 84316848. Its totient is φ = 78833664.

The previous prime is 81555559. The next prime is 81555577. The reversal of 81555563 is 36555518.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81555563 - 2² = 81555559 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81555533) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5606 + ... + 13947.

It is an arithmetic number, because the mean of its divisors is an integer number (10539606).

Almost surely, 2^81555563 is an apocalyptic number.

81555563 is a deficient number, since it is larger than the sum of its proper divisors (2761285).

81555563 is a wasteful number, since it uses less digits than its factorization.

81555563 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19693.

The product of its digits is 90000, while the sum is 38.

The square root of 81555563 is about 9030.8118682652. The cubic root of 81555563 is about 433.6618285623.

The spelling of 81555563 in words is "eighty-one million, five hundred fifty-five thousand, five hundred sixty-three".