221371991657 has 4 divisors (see below), whose sum is σ = 223654177236. Its totient is φ = 219089806080.

The previous prime is 221371991653. The next prime is 221371991663. The reversal of 221371991657 is 756199173122.

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

It can be written as a sum of positive squares in 2 ways, for example, as 130370822761 + 91001168896 = 361069^2 + 301664^2 .

It is a cyclic number.

It is not a de Polignac number, because 221371991657 - 2² = 221371991653 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 221371991599 and 221371991608.

It is not an unprimeable number, because it can be changed into a prime (221371991651) 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, 1141092644 + ... + 1141092837.

It is an arithmetic number, because the mean of its divisors is an integer number (55913544309).

Almost surely, 2^221371991657 is an apocalyptic number.

It is an amenable number.

221371991657 is a deficient number, since it is larger than the sum of its proper divisors (2282185579).

221371991657 is an equidigital number, since it uses as much as digits as its factorization.

221371991657 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2282185578.

The product of its digits is 1428840, while the sum is 53.

The spelling of 221371991657 in words is "two hundred twenty-one billion, three hundred seventy-one million, nine hundred ninety-one thousand, six hundred fifty-seven".