20439557 has 2 divisors, whose sum is σ = 20439558. Its totient is φ = 20439556.

The previous prime is 20439541. The next prime is 20439563. The reversal of 20439557 is 75593402.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11282881 + 9156676 = 3359^2 + 3026^2 .

It is a cyclic number.

It is not a de Polignac number, because 20439557 - 2⁴ = 20439541 is a prime.

It is equal to p_1296656 and since 20439557 and 1296656 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20439257) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10219778 + 10219779.

It is an arithmetic number, because the mean of its divisors is an integer number (10219779).

Almost surely, 2^20439557 is an apocalyptic number.

It is an amenable number.

20439557 is a deficient number, since it is larger than the sum of its proper divisors (1).

20439557 is an equidigital number, since it uses as much as digits as its factorization.

20439557 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 37800, while the sum is 35.

The square root of 20439557 is about 4521.0128290019. The cubic root of 20439557 is about 273.4159375890.

The spelling of 20439557 in words is "twenty million, four hundred thirty-nine thousand, five hundred fifty-seven".