18100821 has 4 divisors (see below), whose sum is σ = 24134432. Its totient is φ = 12067212.

The previous prime is 18100783. The next prime is 18100837. The reversal of 18100821 is 12800181.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12800181 = 3 ⋅4266727.

It is not a de Polignac number, because 18100821 - 2⁶ = 18100757 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 (18100871) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3016801 + ... + 3016806.

It is an arithmetic number, because the mean of its divisors is an integer number (6033608).

Almost surely, 2^18100821 is an apocalyptic number.

It is an amenable number.

18100821 is a deficient number, since it is larger than the sum of its proper divisors (6033611).

18100821 is an equidigital number, since it uses as much as digits as its factorization.

18100821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6033610.

The product of its (nonzero) digits is 128, while the sum is 21.

The square root of 18100821 is about 4254.5059642689. The cubic root of 18100821 is about 262.5625356678.

The spelling of 18100821 in words is "eighteen million, one hundred thousand, eight hundred twenty-one".