81563619 has 4 divisors (see below), whose sum is σ = 108751496. Its totient is φ = 54375744.

The previous prime is 81563609. The next prime is 81563627. The reversal of 81563619 is 91636518.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 81563619 - 2⁷ = 81563491 is a prime.

It is a super-2 number, since 2×81563619² = 13305247888754322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81563609) 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, 13593934 + ... + 13593939.

It is an arithmetic number, because the mean of its divisors is an integer number (27187874).

Almost surely, 2^81563619 is an apocalyptic number.

81563619 is a deficient number, since it is larger than the sum of its proper divisors (27187877).

81563619 is a wasteful number, since it uses less digits than its factorization.

81563619 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27187876.

The product of its digits is 38880, while the sum is 39.

The square root of 81563619 is about 9031.2578858097. The cubic root of 81563619 is about 433.6761070270.

The spelling of 81563619 in words is "eighty-one million, five hundred sixty-three thousand, six hundred nineteen".