91001220221 has 4 divisors (see below), whose sum is σ = 93117527712. Its totient is φ = 88884912732.

The previous prime is 91001220197. The next prime is 91001220287. The reversal of 91001220221 is 12202210019.

It is a happy number.

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 a de Polignac number, because none of the positive numbers 2^k-91001220221 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 91001220193 and 91001220202.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91001210221) 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 3 ways as a sum of consecutive naturals, for example, 1058153681 + ... + 1058153766.

It is an arithmetic number, because the mean of its divisors is an integer number (23279381928).

Almost surely, 2^91001220221 is an apocalyptic number.

It is an amenable number.

91001220221 is a deficient number, since it is larger than the sum of its proper divisors (2116307491).

91001220221 is a wasteful number, since it uses less digits than its factorization.

91001220221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2116307490.

The product of its (nonzero) digits is 144, while the sum is 20.

The spelling of 91001220221 in words is "ninety-one billion, one million, two hundred twenty thousand, two hundred twenty-one".