999993721 has 2 divisors, whose sum is σ = 999993722. Its totient is φ = 999993720.

The previous prime is 999993719. The next prime is 999993733. The reversal of 999993721 is 127399999.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 770895225 + 229098496 = 27765^2 + 15136^2 .

It is a cyclic number.

It is not a de Polignac number, because 999993721 - 2¹ = 999993719 is a prime.

Together with 999993719, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (999993791) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499996860 + 499996861.

It is an arithmetic number, because the mean of its divisors is an integer number (499996861).

Almost surely, 2^999993721 is an apocalyptic number.

It is an amenable number.

999993721 is a deficient number, since it is larger than the sum of its proper divisors (1).

999993721 is an equidigital number, since it uses as much as digits as its factorization.

999993721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2480058, while the sum is 58.

The square root of 999993721 is about 31622.6773218208. The cubic root of 999993721 is about 999.9979069956.

The spelling of 999993721 in words is "nine hundred ninety-nine million, nine hundred ninety-three thousand, seven hundred twenty-one".