231684721 has 4 divisors (see below), whose sum is σ = 245313252. Its totient is φ = 218056192.

The previous prime is 231684709. The next prime is 231684749. The reversal of 231684721 is 127486132.

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 146676321 + 85008400 = 12111^2 + 9220^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-231684721 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (231684751) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6814240 + ... + 6814273.

It is an arithmetic number, because the mean of its divisors is an integer number (61328313).

Almost surely, 2^231684721 is an apocalyptic number.

It is an amenable number.

231684721 is a deficient number, since it is larger than the sum of its proper divisors (13628531).

231684721 is a wasteful number, since it uses less digits than its factorization.

231684721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13628530.

The product of its digits is 16128, while the sum is 34.

The square root of 231684721 is about 15221.1931529693. The cubic root of 231684721 is about 614.1848949969.

It can be divided in two parts, 23168 and 4721, that added together give a square (27889 = 167²).

The spelling of 231684721 in words is "two hundred thirty-one million, six hundred eighty-four thousand, seven hundred twenty-one".