20805213 has 16 divisors (see below), whose sum is σ = 32590656. Its totient is φ = 11639040.

The previous prime is 20805199. The next prime is 20805223. The reversal of 20805213 is 31250802.

It is not a de Polignac number, because 20805213 - 2¹² = 20801117 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20805213.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20805223) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 23820 + ... + 24677.

It is an arithmetic number, because the mean of its divisors is an integer number (2036916).

Almost surely, 2^20805213 is an apocalyptic number.

It is an amenable number.

20805213 is a deficient number, since it is larger than the sum of its proper divisors (11785443).

20805213 is a wasteful number, since it uses less digits than its factorization.

20805213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 48524.

The product of its (nonzero) digits is 480, while the sum is 21.

The square root of 20805213 is about 4561.2731775240. The cubic root of 20805213 is about 275.0367466047.

The spelling of 20805213 in words is "twenty million, eight hundred five thousand, two hundred thirteen".