991210001221 has 4 divisors (see below), whose sum is σ = 1081320001344. Its totient is φ = 901100001100.

The previous prime is 991210001183. The next prime is 991210001231. The reversal of 991210001221 is 122100012199.

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 991210001221 - 2⁹ = 991210000709 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 991210001221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991210001231) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 45055000045 + ... + 45055000066.

It is an arithmetic number, because the mean of its divisors is an integer number (270330000336).

Almost surely, 2^991210001221 is an apocalyptic number.

It is an amenable number.

991210001221 is a deficient number, since it is larger than the sum of its proper divisors (90110000123).

991210001221 is a wasteful number, since it uses less digits than its factorization.

991210001221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 90110000122.

The product of its (nonzero) digits is 648, while the sum is 28.

The spelling of 991210001221 in words is "nine hundred ninety-one billion, two hundred ten million, one thousand, two hundred twenty-one".