21001213 has 4 divisors (see below), whose sum is σ = 22106560. Its totient is φ = 19895868.

The previous prime is 21001187. The next prime is 21001247. The reversal of 21001213 is 31210012.

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 21001213 - 2⁵ = 21001181 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21001213.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21002213) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 552645 + ... + 552682.

It is an arithmetic number, because the mean of its divisors is an integer number (5526640).

Almost surely, 2^21001213 is an apocalyptic number.

It is an amenable number.

21001213 is a deficient number, since it is larger than the sum of its proper divisors (1105347).

21001213 is a wasteful number, since it uses less digits than its factorization.

21001213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1105346.

The product of its (nonzero) digits is 12, while the sum is 10.

The square root of 21001213 is about 4582.7080421951. The cubic root of 21001213 is about 275.8977295597.

Adding to 21001213 its reverse (31210012), we get a palindrome (52211225).

The spelling of 21001213 in words is "twenty-one million, one thousand, two hundred thirteen".