21210345 has 36 divisors (see below), whose sum is σ = 39824460. Its totient is φ = 10438272.

The previous prime is 21210337. The next prime is 21210367. The reversal of 21210345 is 54301212.

It can be written as a sum of positive squares in 6 ways, for example, as 3164841 + 18045504 = 1779^2 + 4248^2 .

It is not a de Polignac number, because 21210345 - 2³ = 21210337 is a prime.

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

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 6211 + ... + 8999.

It is an arithmetic number, because the mean of its divisors is an integer number (1106235).

Almost surely, 2^21210345 is an apocalyptic number.

It is an amenable number.

21210345 is a deficient number, since it is larger than the sum of its proper divisors (18614115).

21210345 is a wasteful number, since it uses less digits than its factorization.

21210345 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2826 (or 2810 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 21210345 is about 4605.4690314885. The cubic root of 21210345 is about 276.8105113188.

Adding to 21210345 its reverse (54301212), we get a palindrome (75511557).

The spelling of 21210345 in words is "twenty-one million, two hundred ten thousand, three hundred forty-five".