321720545 has 4 divisors (see below), whose sum is σ = 386064660. Its totient is φ = 257376432.

The previous prime is 321720523. The next prime is 321720557. The reversal of 321720545 is 545027123.

It is a happy number.

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 118287376 + 203433169 = 10876^2 + 14263^2 .

It is a cyclic number.

It is not a de Polignac number, because 321720545 - 2²² = 317526241 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 32172050 + ... + 32172059.

It is an arithmetic number, because the mean of its divisors is an integer number (96516165).

Almost surely, 2^321720545 is an apocalyptic number.

It is an amenable number.

321720545 is a deficient number, since it is larger than the sum of its proper divisors (64344115).

321720545 is an equidigital number, since it uses as much as digits as its factorization.

321720545 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 64344114.

The product of its (nonzero) digits is 8400, while the sum is 29.

The square root of 321720545 is about 17936.5700455801. The cubic root of 321720545 is about 685.2140592305.

Adding to 321720545 its reverse (545027123), we get a palindrome (866747668).

The spelling of 321720545 in words is "three hundred twenty-one million, seven hundred twenty thousand, five hundred forty-five".