81222636021 has 4 divisors (see below), whose sum is σ = 108296848032. Its totient is φ = 54148424012.

The previous prime is 81222636013. The next prime is 81222636073. The reversal of 81222636021 is 12063622218.

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 81222636021 - 2³ = 81222636013 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81222636821) 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, 13537106001 + ... + 13537106006.

It is an arithmetic number, because the mean of its divisors is an integer number (27074212008).

Almost surely, 2^81222636021 is an apocalyptic number.

It is an amenable number.

81222636021 is a deficient number, since it is larger than the sum of its proper divisors (27074212011).

81222636021 is a wasteful number, since it uses less digits than its factorization.

81222636021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27074212010.

The product of its (nonzero) digits is 13824, while the sum is 33.

The spelling of 81222636021 in words is "eighty-one billion, two hundred twenty-two million, six hundred thirty-six thousand, twenty-one".