221208731 has 4 divisors (see below), whose sum is σ = 221251200. Its totient is φ = 221166264.

The previous prime is 221208719. The next prime is 221208763. The reversal of 221208731 is 137802122.

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 221208731 - 2⁶ = 221208667 is a prime.

It is a super-2 number, since 2×221208731² = 97866605341260722, which contains 22 as substring.

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 221208731.

It is not an unprimeable number, because it can be changed into a prime (221208331) 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, 12116 + ... + 24273.

It is an arithmetic number, because the mean of its divisors is an integer number (55312800).

Almost surely, 2^221208731 is an apocalyptic number.

221208731 is a deficient number, since it is larger than the sum of its proper divisors (42469).

221208731 is an equidigital number, since it uses as much as digits as its factorization.

221208731 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42468.

The product of its (nonzero) digits is 1344, while the sum is 26.

The square root of 221208731 is about 14873.0874736888. The cubic root of 221208731 is about 604.7846429731.

The spelling of 221208731 in words is "two hundred twenty-one million, two hundred eight thousand, seven hundred thirty-one".