81221764101 has 4 divisors (see below), whose sum is σ = 108295685472. Its totient is φ = 54147842732.

The previous prime is 81221764097. The next prime is 81221764121. The reversal of 81221764101 is 10146712218.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81221764101 - 2² = 81221764097 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81221764121) 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, 13536960681 + ... + 13536960686.

It is an arithmetic number, because the mean of its divisors is an integer number (27073921368).

Almost surely, 2^81221764101 is an apocalyptic number.

It is an amenable number.

81221764101 is a deficient number, since it is larger than the sum of its proper divisors (27073921371).

81221764101 is a wasteful number, since it uses less digits than its factorization.

81221764101 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27073921370.

The product of its (nonzero) digits is 5376, while the sum is 33.

The spelling of 81221764101 in words is "eighty-one billion, two hundred twenty-one million, seven hundred sixty-four thousand, one hundred one".