20640331 has 2 divisors, whose sum is σ = 20640332. Its totient is φ = 20640330.

The previous prime is 20640317. The next prime is 20640391. The reversal of 20640331 is 13304602.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20640331 - 2⁵ = 20640299 is a prime.

It is a super-2 number, since 2×20640331² = 852046527579122, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 20640299 and 20640308.

It is not a weakly prime, because it can be changed into another prime (20640391) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10320165 + 10320166.

It is an arithmetic number, because the mean of its divisors is an integer number (10320166).

Almost surely, 2^20640331 is an apocalyptic number.

20640331 is a deficient number, since it is larger than the sum of its proper divisors (1).

20640331 is an equidigital number, since it uses as much as digits as its factorization.

20640331 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 432, while the sum is 19.

The square root of 20640331 is about 4543.1631051504. The cubic root of 20640331 is about 274.3082603434.

Adding to 20640331 its reverse (13304602), we get a palindrome (33944933).

The spelling of 20640331 in words is "twenty million, six hundred forty thousand, three hundred thirty-one".