221311691 has 4 divisors (see below), whose sum is σ = 224343432. Its totient is φ = 218279952.

The previous prime is 221311687. The next prime is 221311693. The reversal of 221311691 is 196113122.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 221311691 - 2² = 221311687 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 221311691.

It is not an unprimeable number, because it can be changed into a prime (221311693) 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, 1515761 + ... + 1515906.

It is an arithmetic number, because the mean of its divisors is an integer number (56085858).

Almost surely, 2^221311691 is an apocalyptic number.

221311691 is a deficient number, since it is larger than the sum of its proper divisors (3031741).

221311691 is an equidigital number, since it uses as much as digits as its factorization.

221311691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3031740.

The product of its digits is 648, while the sum is 26.

The square root of 221311691 is about 14876.5483563897. The cubic root of 221311691 is about 604.8784592950.

The spelling of 221311691 in words is "two hundred twenty-one million, three hundred eleven thousand, six hundred ninety-one".