99900021 has 16 divisors (see below), whose sum is σ = 143675840. Its totient is φ = 61378560.

The previous prime is 99900013. The next prime is 99900029. The reversal of 99900021 is 12000999.

It is an interprime number because it is at equal distance from previous prime (99900013) and next prime (99900029).

It is not a de Polignac number, because 99900021 - 2³ = 99900013 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (99900029) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 28326 + ... + 31656.

It is an arithmetic number, because the mean of its divisors is an integer number (8979740).

Almost surely, 2^99900021 is an apocalyptic number.

It is an amenable number.

99900021 is a deficient number, since it is larger than the sum of its proper divisors (43775819).

99900021 is a wasteful number, since it uses less digits than its factorization.

99900021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4116.

The product of its (nonzero) digits is 1458, while the sum is 30.

The square root of 99900021 is about 9994.9997998999. Note that the first 3 decimals coincide. The cubic root of 99900021 is about 464.0041446444.

The spelling of 99900021 in words is "ninety-nine million, nine hundred thousand, twenty-one".