321720247 has 4 divisors (see below), whose sum is σ = 322198960. Its totient is φ = 321241536.

The previous prime is 321720239. The next prime is 321720307. The reversal of 321720247 is 742027123.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 742027123 = 829 ⋅895087.

It is a cyclic number.

It is not a de Polignac number, because 321720247 - 2³ = 321720239 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (321720227) 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, 238347 + ... + 239692.

It is an arithmetic number, because the mean of its divisors is an integer number (80549740).

Almost surely, 2^321720247 is an apocalyptic number.

321720247 is a deficient number, since it is larger than the sum of its proper divisors (478713).

321720247 is an equidigital number, since it uses as much as digits as its factorization.

321720247 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 478712.

The product of its (nonzero) digits is 4704, while the sum is 28.

The square root of 321720247 is about 17936.5617385273. The cubic root of 321720247 is about 685.2138476661.

The spelling of 321720247 in words is "three hundred twenty-one million, seven hundred twenty thousand, two hundred forty-seven".