99921509 has 2 divisors, whose sum is σ = 99921510. Its totient is φ = 99921508.

The previous prime is 99921473. The next prime is 99921517. The reversal of 99921509 is 90512999.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 82864609 + 17056900 = 9103^2 + 4130^2 .

It is a cyclic number.

It is not a de Polignac number, because 99921509 - 2¹² = 99917413 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 99921509.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (99921109) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 49960754 + 49960755.

It is an arithmetic number, because the mean of its divisors is an integer number (49960755).

Almost surely, 2^99921509 is an apocalyptic number.

It is an amenable number.

99921509 is a deficient number, since it is larger than the sum of its proper divisors (1).

99921509 is an equidigital number, since it uses as much as digits as its factorization.

99921509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 65610, while the sum is 44.

The square root of 99921509 is about 9996.0746795930. The cubic root of 99921509 is about 464.0374105910.

Subtracting from 99921509 its product of nonzero digits (65610), we obtain a palindrome (99855899).

The spelling of 99921509 in words is "ninety-nine million, nine hundred twenty-one thousand, five hundred nine".