81563645 has 8 divisors (see below), whose sum is σ = 97943256. Its totient is φ = 65206336.

The previous prime is 81563633. The next prime is 81563653. The reversal of 81563645 is 54636518.

It can be written as a sum of positive squares in 4 ways, for example, as 31125241 + 50438404 = 5579^2 + 7102^2 .

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 81563645 - 2¹² = 81559549 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81563599 and 81563608.

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, 3959 + ... + 13371.

It is an arithmetic number, because the mean of its divisors is an integer number (12242907).

Almost surely, 2^81563645 is an apocalyptic number.

It is an amenable number.

81563645 is a deficient number, since it is larger than the sum of its proper divisors (16379611).

81563645 is a wasteful number, since it uses less digits than its factorization.

81563645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11151.

The product of its digits is 86400, while the sum is 38.

The square root of 81563645 is about 9031.2593252547. The cubic root of 81563645 is about 433.6761531079.

The spelling of 81563645 in words is "eighty-one million, five hundred sixty-three thousand, six hundred forty-five".