20420557 has 2 divisors, whose sum is σ = 20420558. Its totient is φ = 20420556.

The previous prime is 20420531. The next prime is 20420563. The reversal of 20420557 is 75502402.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17255716 + 3164841 = 4154^2 + 1779^2 .

It is a cyclic number.

It is not a de Polignac number, because 20420557 - 2¹¹ = 20418509 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20420567) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10210278 + 10210279.

It is an arithmetic number, because the mean of its divisors is an integer number (10210279).

Almost surely, 2^20420557 is an apocalyptic number.

It is an amenable number.

20420557 is a deficient number, since it is larger than the sum of its proper divisors (1).

20420557 is an equidigital number, since it uses as much as digits as its factorization.

20420557 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2800, while the sum is 25.

The square root of 20420557 is about 4518.9110413904. The cubic root of 20420557 is about 273.3311915689.

Adding to 20420557 its reverse (75502402), we get a palindrome (95922959).

The spelling of 20420557 in words is "twenty million, four hundred twenty thousand, five hundred fifty-seven".