221506643 has 4 divisors (see below), whose sum is σ = 221653608. Its totient is φ = 221359680.

The previous prime is 221506609. The next prime is 221506667. The reversal of 221506643 is 346605122.

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 221506643 - 2²⁰ = 220458067 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (221506673) 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, 71198 + ... + 74243.

It is an arithmetic number, because the mean of its divisors is an integer number (55413402).

Almost surely, 2^221506643 is an apocalyptic number.

221506643 is a deficient number, since it is larger than the sum of its proper divisors (146965).

221506643 is a wasteful number, since it uses less digits than its factorization.

221506643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 146964.

The product of its (nonzero) digits is 8640, while the sum is 29.

The square root of 221506643 is about 14883.0992404136. The cubic root of 221506643 is about 605.0560183086.

The spelling of 221506643 in words is "two hundred twenty-one million, five hundred six thousand, six hundred forty-three".