67720321 has 2 divisors, whose sum is σ = 67720322. Its totient is φ = 67720320.

The previous prime is 67720243. The next prime is 67720339. The reversal of 67720321 is 12302776.

67720321 is nontrivially palindromic in base 2.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 67650625 + 69696 = 8225^2 + 264^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-67720321 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 67720321.

It is not a weakly prime, because it can be changed into another prime (67720391) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33860160 + 33860161.

It is an arithmetic number, because the mean of its divisors is an integer number (33860161).

Almost surely, 2^67720321 is an apocalyptic number.

It is an amenable number.

67720321 is a deficient number, since it is larger than the sum of its proper divisors (1).

67720321 is an equidigital number, since it uses as much as digits as its factorization.

67720321 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3528, while the sum is 28.

The square root of 67720321 is about 8229.2357482332. The cubic root of 67720321 is about 407.6051563463.

The spelling of 67720321 in words is "sixty-seven million, seven hundred twenty thousand, three hundred twenty-one".