81646561453 has 4 divisors (see below), whose sum is σ = 86449300380. Its totient is φ = 76843822528.

The previous prime is 81646561433. The next prime is 81646561463. The reversal of 81646561453 is 35416564618.

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

It can be written as a sum of positive squares in 2 ways, for example, as 61592319684 + 20054241769 = 248178^2 + 141613^2 .

It is a cyclic number.

It is not a de Polignac number, because 81646561453 - 2¹⁷ = 81646430381 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81646561397 and 81646561406.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81646561433) 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, 2401369438 + ... + 2401369471.

It is an arithmetic number, because the mean of its divisors is an integer number (21612325095).

Almost surely, 2^81646561453 is an apocalyptic number.

It is an amenable number.

81646561453 is a deficient number, since it is larger than the sum of its proper divisors (4802738927).

81646561453 is a wasteful number, since it uses less digits than its factorization.

81646561453 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4802738926.

The product of its digits is 2073600, while the sum is 49.

The spelling of 81646561453 in words is "eighty-one billion, six hundred forty-six million, five hundred sixty-one thousand, four hundred fifty-three".