321012721 has 4 divisors (see below), whose sum is σ = 322390692. Its totient is φ = 319634752.

The previous prime is 321012701. The next prime is 321012761. The reversal of 321012721 is 127210123.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 127210123 = 53 ⋅2400191.

It can be written as a sum of positive squares in 2 ways, for example, as 104775696 + 216237025 = 10236^2 + 14705^2 .

It is a cyclic number.

It is not a de Polignac number, because 321012721 - 2²⁵ = 287458289 is a prime.

It is an alternating number because its digits alternate between odd and even.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (321012701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 688636 + ... + 689101.

It is an arithmetic number, because the mean of its divisors is an integer number (80597673).

Almost surely, 2^321012721 is an apocalyptic number.

It is an amenable number.

321012721 is a deficient number, since it is larger than the sum of its proper divisors (1377971).

321012721 is a wasteful number, since it uses less digits than its factorization.

321012721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1377970.

The product of its (nonzero) digits is 168, while the sum is 19.

The square root of 321012721 is about 17916.8278721430. The cubic root of 321012721 is about 684.7111723893.

Adding to 321012721 its reverse (127210123), we get a palindrome (448222844).

It can be divided in two parts, 3210 and 12721, that added together give a triangular number (15931 = T₁₇₈).

The spelling of 321012721 in words is "three hundred twenty-one million, twelve thousand, seven hundred twenty-one".