21213351 has 6 divisors (see below), whose sum is σ = 30641520. Its totient is φ = 14142228.

The previous prime is 21213349. The next prime is 21213373. The reversal of 21213351 is 15331212.

It is not a de Polignac number, because 21213351 - 2¹ = 21213349 is a prime.

It is a congruent number.

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 5 ways as a sum of consecutive naturals, for example, 1178511 + ... + 1178528.

It is an arithmetic number, because the mean of its divisors is an integer number (5106920).

Almost surely, 2^21213351 is an apocalyptic number.

21213351 is a deficient number, since it is larger than the sum of its proper divisors (9428169).

21213351 is a wasteful number, since it uses less digits than its factorization.

21213351 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2357045 (or 2357042 counting only the distinct ones).

The product of its digits is 180, while the sum is 18.

The square root of 21213351 is about 4605.7953710516. The cubic root of 21213351 is about 276.8235875338.

Adding to 21213351 its reverse (15331212), we get a palindrome (36544563).

The spelling of 21213351 in words is "twenty-one million, two hundred thirteen thousand, three hundred fifty-one".