21018349 has 4 divisors (see below), whose sum is σ = 22929120. Its totient is φ = 19107580.

The previous prime is 21018323. The next prime is 21018397. The reversal of 21018349 is 94381012.

It is a happy number.

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 a cyclic number.

It is not a de Polignac number, because 21018349 - 2⁵ = 21018317 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21018149) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 955369 + ... + 955390.

It is an arithmetic number, because the mean of its divisors is an integer number (5732280).

Almost surely, 2^21018349 is an apocalyptic number.

It is an amenable number.

21018349 is a deficient number, since it is larger than the sum of its proper divisors (1910771).

21018349 is a wasteful number, since it uses less digits than its factorization.

21018349 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1910770.

The product of its (nonzero) digits is 1728, while the sum is 28.

The square root of 21018349 is about 4584.5772978542. The cubic root of 21018349 is about 275.9727490073.

The spelling of 21018349 in words is "twenty-one million, eighteen thousand, three hundred forty-nine".