81224007709 has 4 divisors (see below), whose sum is σ = 87472008316. Its totient is φ = 74976007104.

The previous prime is 81224007707. The next prime is 81224007713. The reversal of 81224007709 is 90770042218.

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 40191428484 + 41032579225 = 200478^2 + 202565^2 .

It is a cyclic number.

It is not a de Polignac number, because 81224007709 - 2¹ = 81224007707 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81224007701) 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, 3124000284 + ... + 3124000309.

It is an arithmetic number, because the mean of its divisors is an integer number (21868002079).

Almost surely, 2^81224007709 is an apocalyptic number.

It is an amenable number.

81224007709 is a deficient number, since it is larger than the sum of its proper divisors (6248000607).

81224007709 is a wasteful number, since it uses less digits than its factorization.

81224007709 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6248000606.

The product of its (nonzero) digits is 56448, while the sum is 40.

The spelling of 81224007709 in words is "eighty-one billion, two hundred twenty-four million, seven thousand, seven hundred nine".