18121213 has 4 divisors (see below), whose sum is σ = 19768608. Its totient is φ = 16473820.

The previous prime is 18121211. The next prime is 18121237. The reversal of 18121213 is 31212181.

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.

It is not a de Polignac number, because 18121213 - 2¹ = 18121211 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 (18121211) 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, 823681 + ... + 823702.

It is an arithmetic number, because the mean of its divisors is an integer number (4942152).

Almost surely, 2^18121213 is an apocalyptic number.

It is an amenable number.

18121213 is a deficient number, since it is larger than the sum of its proper divisors (1647395).

18121213 is a wasteful number, since it uses less digits than its factorization.

18121213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1647394.

The product of its digits is 96, while the sum is 19.

The square root of 18121213 is about 4256.9018076531. The cubic root of 18121213 is about 262.6610977873.

Adding to 18121213 its reverse (31212181), we get a palindrome (49333394).

It can be divided in two parts, 1812 and 1213, that added together give a square (3025 = 55²).

The spelling of 18121213 in words is "eighteen million, one hundred twenty-one thousand, two hundred thirteen".