20687213 has 4 divisors (see below), whose sum is σ = 20697600. Its totient is φ = 20676828.

The previous prime is 20687207. The next prime is 20687243. The reversal of 20687213 is 31278602.

It is a happy number.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 20687213 - 2⁴ = 20687197 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20687203) 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, 1163 + ... + 6536.

It is an arithmetic number, because the mean of its divisors is an integer number (5174400).

Almost surely, 2^20687213 is an apocalyptic number.

It is an amenable number.

20687213 is a deficient number, since it is larger than the sum of its proper divisors (10387).

20687213 is an equidigital number, since it uses as much as digits as its factorization.

20687213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10386.

The product of its (nonzero) digits is 4032, while the sum is 29.

The square root of 20687213 is about 4548.3197996623. The cubic root of 20687213 is about 274.5157892407.

The spelling of 20687213 in words is "twenty million, six hundred eighty-seven thousand, two hundred thirteen".