81222709 has 4 divisors (see below), whose sum is σ = 81241804. Its totient is φ = 81203616.

The previous prime is 81222703. The next prime is 81222797. The reversal of 81222709 is 90722218.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 90722218 = 2 ⋅45361109.

It can be written as a sum of positive squares in 2 ways, for example, as 6140484 + 75082225 = 2478^2 + 8665^2 .

It is a cyclic number.

It is not a de Polignac number, because 81222709 - 2¹³ = 81214517 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 (81222703) 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, 49 + ... + 12745.

It is an arithmetic number, because the mean of its divisors is an integer number (20310451).

Almost surely, 2^81222709 is an apocalyptic number.

It is an amenable number.

81222709 is a deficient number, since it is larger than the sum of its proper divisors (19095).

81222709 is a wasteful number, since it uses less digits than its factorization.

81222709 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19094.

The product of its (nonzero) digits is 4032, while the sum is 31.

The square root of 81222709 is about 9012.3642292131. The cubic root of 81222709 is about 433.0710538422.

The spelling of 81222709 in words is "eighty-one million, two hundred twenty-two thousand, seven hundred nine".