21251213 has 8 divisors (see below), whose sum is σ = 22108416. Its totient is φ = 20404800.

The previous prime is 21251201. The next prime is 21251239. The reversal of 21251213 is 31215212.

21251213 = T₃₈₂ + T₃₈₃ + ... + T₅₆₇.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21251213 is a prime.

It is a super-2 number, since 2×21251213² = 903228107942738, which contains 22 as substring.

It is a Duffinian number.

It is a plaindrome in base 16.

It is a junction number, because it is equal to n+sod(n) for n = 21251191 and 21251200.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21251413) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1445 + ... + 6677.

It is an arithmetic number, because the mean of its divisors is an integer number (2763552).

Almost surely, 2^21251213 is an apocalyptic number.

It is an amenable number.

21251213 is a deficient number, since it is larger than the sum of its proper divisors (857203).

21251213 is a wasteful number, since it uses less digits than its factorization.

21251213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5395.

The product of its digits is 120, while the sum is 17.

The square root of 21251213 is about 4609.9037950916. The cubic root of 21251213 is about 276.9881830162.

Adding to 21251213 its reverse (31215212), we get a palindrome (52466425).

The spelling of 21251213 in words is "twenty-one million, two hundred fifty-one thousand, two hundred thirteen".