99901721 has 2 divisors, whose sum is σ = 99901722. Its totient is φ = 99901720.

The previous prime is 99901693. The next prime is 99901759. The reversal of 99901721 is 12710999.

It is an a-pointer prime, because the next prime (99901759) can be obtained adding 99901721 to its sum of digits (38).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 86862400 + 13039321 = 9320^2 + 3611^2 .

It is a cyclic number.

It is not a de Polignac number, because 99901721 - 2²⁶ = 32792857 is a prime.

It is equal to p_5756087 and since 99901721 and 5756087 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (99901421) 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 as a sum of consecutive naturals, namely, 49950860 + 49950861.

It is an arithmetic number, because the mean of its divisors is an integer number (49950861).

Almost surely, 2^99901721 is an apocalyptic number.

It is an amenable number.

99901721 is a deficient number, since it is larger than the sum of its proper divisors (1).

99901721 is an equidigital number, since it uses as much as digits as its factorization.

99901721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 10206, while the sum is 38.

The square root of 99901721 is about 9995.0848420611. The cubic root of 99901721 is about 464.0067766177.

It can be divided in two parts, 9990 and 1721, that added together give a palindrome (11711).

The spelling of 99901721 in words is "ninety-nine million, nine hundred one thousand, seven hundred twenty-one".