421000721 has 2 divisors, whose sum is σ = 421000722. Its totient is φ = 421000720.

The previous prime is 421000691. The next prime is 421000753. The reversal of 421000721 is 127000124.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 374964496 + 46036225 = 19364^2 + 6785^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-421000721 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 421000721.

It is not a weakly prime, because it can be changed into another prime (421000771) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 210500360 + 210500361.

It is an arithmetic number, because the mean of its divisors is an integer number (210500361).

Almost surely, 2^421000721 is an apocalyptic number.

It is an amenable number.

421000721 is a deficient number, since it is larger than the sum of its proper divisors (1).

421000721 is an equidigital number, since it uses as much as digits as its factorization.

421000721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 112, while the sum is 17.

The square root of 421000721 is about 20518.3020983706. The cubic root of 421000721 is about 749.4815504367.

Adding to 421000721 its reverse (127000124), we get a palindrome (548000845).

The spelling of 421000721 in words is "four hundred twenty-one million, seven hundred twenty-one", and thus it is an aban number.