99999721 has 2 divisors, whose sum is σ = 99999722.
Its totient is φ = 99999720.
The previous prime is 99999703. The next prime is 99999773. The reversal of 99999721 is 12799999.
It is a weak prime.
It can be written as a sum of positive squares in only one way, i.e., 60762025 + 39237696 = 7795^2 + 6264^2
It is a cyclic number.
It is not a de Polignac number, because 99999721 - 225 = 66445289 is a prime.
It is a Chen prime.
It is a nialpdrome in base 10.
It is not a weakly prime, because it can be changed into another prime (99999821) by changing a digit.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 49999860 + 49999861.
It is an arithmetic number, because the mean of its divisors is an integer number (49999861).
Almost surely, 299999721 is an apocalyptic number.
It is an amenable number.
99999721 is a deficient number, since it is larger than the sum of its proper divisors (1).
99999721 is an equidigital number, since it uses as much as digits as its factorization.
99999721 is an evil number, because the sum of its binary digits is even.
The product of its digits is 826686, while the sum is 55.
The square root of 99999721 is about 9999.9860499903.
The cubic root of 99999721 is about 464.1584516931.
It can be divided in two parts, 9999 and 9721, that multiplied together give a palindrome (97200279).
The spelling of 99999721 in words is "ninety-nine million, nine hundred ninety-nine thousand, seven hundred twenty-one".