81220742457 has 8 divisors (see below), whose sum is σ = 108361971360. Its totient is φ = 54113337600.

The previous prime is 81220742387. The next prime is 81220742459. The reversal of 81220742457 is 75424702218.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81220742457 - 2¹⁶ = 81220676921 is a prime.

It is a Smith number, since the sum of its digits (42) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (81220742459) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8450407 + ... + 8460012.

It is an arithmetic number, because the mean of its divisors is an integer number (13545246420).

Almost surely, 2^81220742457 is an apocalyptic number.

It is an amenable number.

81220742457 is a deficient number, since it is larger than the sum of its proper divisors (27141228903).

81220742457 is a wasteful number, since it uses less digits than its factorization.

81220742457 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16912023.

The product of its (nonzero) digits is 250880, while the sum is 42.

The spelling of 81220742457 in words is "eighty-one billion, two hundred twenty million, seven hundred forty-two thousand, four hundred fifty-seven".