99815821 has 8 divisors (see below), whose sum is σ = 114776384. Its totient is φ = 85030560.

The previous prime is 99815803. The next prime is 99815839. The reversal of 99815821 is 12851899.

It is an interprime number because it is at equal distance from previous prime (99815803) and next prime (99815839).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a 12-Lehmer number, since φ(99815821) divides (99815821-1)¹².

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-99815821 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (99815851) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 42600 + ... + 44881.

It is an arithmetic number, because the mean of its divisors is an integer number (14347048).

Almost surely, 2^99815821 is an apocalyptic number.

It is an amenable number.

99815821 is a deficient number, since it is larger than the sum of its proper divisors (14960563).

99815821 is a wasteful number, since it uses less digits than its factorization.

99815821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87651.

The product of its digits is 51840, while the sum is 43.

The square root of 99815821 is about 9990.7868058527. The cubic root of 99815821 is about 463.8737471726.

The spelling of 99815821 in words is "ninety-nine million, eight hundred fifteen thousand, eight hundred twenty-one".