221001221091 has 16 divisors (see below), whose sum is σ = 336994630400. Its totient is φ = 126199837728.

The previous prime is 221001221087. The next prime is 221001221099. The reversal of 221001221091 is 190122100122.

It is not a de Polignac number, because 221001221091 - 2² = 221001221087 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (221001221099) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3575896 + ... + 3637173.

It is an arithmetic number, because the mean of its divisors is an integer number (21062164400).

Almost surely, 2^221001221091 is an apocalyptic number.

221001221091 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

221001221091 is a deficient number, since it is larger than the sum of its proper divisors (115993409309).

221001221091 is a wasteful number, since it uses less digits than its factorization.

221001221091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7214538.

The product of its (nonzero) digits is 144, while the sum is 21.

The spelling of 221001221091 in words is "two hundred twenty-one billion, one million, two hundred twenty-one thousand, ninety-one".