21010813 has 4 divisors (see below), whose sum is σ = 21053088. Its totient is φ = 20968540.

The previous prime is 21010811. The next prime is 21010831. The reversal of 21010813 is 31801012.

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 21010813 - 2¹ = 21010811 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21010811) 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, 20383 + ... + 21388.

It is an arithmetic number, because the mean of its divisors is an integer number (5263272).

Almost surely, 2^21010813 is an apocalyptic number.

It is an amenable number.

21010813 is a deficient number, since it is larger than the sum of its proper divisors (42275).

21010813 is an equidigital number, since it uses as much as digits as its factorization.

21010813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42274.

The product of its (nonzero) digits is 48, while the sum is 16.

The square root of 21010813 is about 4583.7553381480. The cubic root of 21010813 is about 275.9397622863.

Adding to 21010813 its reverse (31801012), we get a palindrome (52811825).

The spelling of 21010813 in words is "twenty-one million, ten thousand, eight hundred thirteen".