20001557 has 2 divisors, whose sum is σ = 20001558. Its totient is φ = 20001556.

The previous prime is 20001551. The next prime is 20001613. The reversal of 20001557 is 75510002.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17648401 + 2353156 = 4201^2 + 1534^2 .

It is a cyclic number.

It is not a de Polignac number, because 20001557 - 2⁸ = 20001301 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20001551) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10000778 + 10000779.

It is an arithmetic number, because the mean of its divisors is an integer number (10000779).

Almost surely, 2^20001557 is an apocalyptic number.

It is an amenable number.

20001557 is a deficient number, since it is larger than the sum of its proper divisors (1).

20001557 is an equidigital number, since it uses as much as digits as its factorization.

20001557 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 350, while the sum is 20.

The square root of 20001557 is about 4472.3100295038. The cubic root of 20001557 is about 271.4488053904.

Adding to 20001557 its reverse (75510002), we get a palindrome (95511559).

The spelling of 20001557 in words is "twenty million, one thousand, five hundred fifty-seven".