20640401 has 2 divisors, whose sum is σ = 20640402. Its totient is φ = 20640400.

The previous prime is 20640391. The next prime is 20640437. The reversal of 20640401 is 10404602.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18284176 + 2356225 = 4276^2 + 1535^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20640401 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 20640401.

It is not a weakly prime, because it can be changed into another prime (20640001) 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 as a sum of consecutive naturals, namely, 10320200 + 10320201.

It is an arithmetic number, because the mean of its divisors is an integer number (10320201).

Almost surely, 2^20640401 is an apocalyptic number.

It is an amenable number.

20640401 is a deficient number, since it is larger than the sum of its proper divisors (1).

20640401 is an equidigital number, since it uses as much as digits as its factorization.

20640401 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 192, while the sum is 17.

The square root of 20640401 is about 4543.1708090275. The cubic root of 20640401 is about 274.3085704411.

The spelling of 20640401 in words is "twenty million, six hundred forty thousand, four hundred one".