81553645 has 8 divisors (see below), whose sum is σ = 99469080. Its totient is φ = 64173120.

The previous prime is 81553621. The next prime is 81553651. The reversal of 81553645 is 54635518.

It can be written as a sum of positive squares in 4 ways, for example, as 11964681 + 69588964 = 3459^2 + 8342^2 .

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

It is not a de Polignac number, because 81553645 - 2⁵ = 81553613 is a prime.

It is a super-3 number, since 3×81553645³ (a number of 25 digits) contains 333 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 133390 + ... + 133999.

It is an arithmetic number, because the mean of its divisors is an integer number (12433635).

Almost surely, 2^81553645 is an apocalyptic number.

It is an amenable number.

81553645 is a deficient number, since it is larger than the sum of its proper divisors (17915435).

81553645 is a wasteful number, since it uses less digits than its factorization.

81553645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 267455.

The product of its digits is 72000, while the sum is 37.

The square root of 81553645 is about 9030.7056756380. The cubic root of 81553645 is about 433.6584289581.

The spelling of 81553645 in words is "eighty-one million, five hundred fifty-three thousand, six hundred forty-five".