99981421 has 2 divisors, whose sum is σ = 99981422. Its totient is φ = 99981420.

The previous prime is 99981389. The next prime is 99981451. The reversal of 99981421 is 12418999.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 60668521 + 39312900 = 7789^2 + 6270^2 .

It is an emirp because it is prime and its reverse (12418999) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 99981421 - 2⁵ = 99981389 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (99981451) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 49990710 + 49990711.

It is an arithmetic number, because the mean of its divisors is an integer number (49990711).

Almost surely, 2^99981421 is an apocalyptic number.

It is an amenable number.

99981421 is a deficient number, since it is larger than the sum of its proper divisors (1).

99981421 is an equidigital number, since it uses as much as digits as its factorization.

99981421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 46656, while the sum is 43.

The square root of 99981421 is about 9999.0710068486. The cubic root of 99981421 is about 464.1301362212.

The spelling of 99981421 in words is "ninety-nine million, nine hundred eighty-one thousand, four hundred twenty-one".