21213345 has 16 divisors (see below), whose sum is σ = 34015680. Its totient is φ = 11289024.

The previous prime is 21213343. The next prime is 21213347. The reversal of 21213345 is 54331212.

It is an interprime number because it is at equal distance from previous prime (21213343) and next prime (21213347).

It is not a de Polignac number, because 21213345 - 2¹ = 21213343 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21213341) 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, 7086 + ... + 9624.

It is an arithmetic number, because the mean of its divisors is an integer number (2125980).

Almost surely, 2^21213345 is an apocalyptic number.

It is an amenable number.

21213345 is a deficient number, since it is larger than the sum of its proper divisors (12802335).

21213345 is a wasteful number, since it uses less digits than its factorization.

21213345 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3104.

The product of its digits is 720, while the sum is 21.

The square root of 21213345 is about 4605.7947196982. The cubic root of 21213345 is about 276.8235614348.

Adding to 21213345 its reverse (54331212), we get a palindrome (75544557).

The spelling of 21213345 in words is "twenty-one million, two hundred thirteen thousand, three hundred forty-five".