20520391 has 4 divisors (see below), whose sum is σ = 20596384. Its totient is φ = 20444400.

The previous prime is 20520389. The next prime is 20520403. The reversal of 20520391 is 19302502.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20520391 - 2¹ = 20520389 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 (20520191) 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, 37590 + ... + 38131.

It is an arithmetic number, because the mean of its divisors is an integer number (5149096).

Almost surely, 2^20520391 is an apocalyptic number.

20520391 is a deficient number, since it is larger than the sum of its proper divisors (75993).

20520391 is an equidigital number, since it uses as much as digits as its factorization.

20520391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 75992.

The product of its (nonzero) digits is 540, while the sum is 22.

The square root of 20520391 is about 4529.9438186362. The cubic root of 20520391 is about 273.7758969961.

Adding to 20520391 its reverse (19302502), we get a palindrome (39822893).

The spelling of 20520391 in words is "twenty million, five hundred twenty thousand, three hundred ninety-one".