20731213 has 4 divisors (see below), whose sum is σ = 20855520. Its totient is φ = 20606908.

The previous prime is 20731189. The next prime is 20731231. The reversal of 20731213 is 31213702.

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 a de Polignac number, because none of the positive numbers 2^k-20731213 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 (20731253) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 61903 + ... + 62236.

It is an arithmetic number, because the mean of its divisors is an integer number (5213880).

Almost surely, 2^20731213 is an apocalyptic number.

It is an amenable number.

20731213 is a deficient number, since it is larger than the sum of its proper divisors (124307).

20731213 is a wasteful number, since it uses less digits than its factorization.

20731213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 124306.

The product of its (nonzero) digits is 252, while the sum is 19.

The square root of 20731213 is about 4553.1541814439. The cubic root of 20731213 is about 274.7102755862.

Adding to 20731213 its reverse (31213702), we get a palindrome (51944915).

The spelling of 20731213 in words is "twenty million, seven hundred thirty-one thousand, two hundred thirteen".