20642257 has 2 divisors, whose sum is σ = 20642258. Its totient is φ = 20642256.

The previous prime is 20642239. The next prime is 20642269. The reversal of 20642257 is 75224602.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18671041 + 1971216 = 4321^2 + 1404^2 .

It is a cyclic number.

It is not a de Polignac number, because 20642257 - 2⁷ = 20642129 is a prime.

It is a super-2 number, since 2×20642257² = 852205548108098, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (20642057) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10321128 + 10321129.

It is an arithmetic number, because the mean of its divisors is an integer number (10321129).

Almost surely, 2^20642257 is an apocalyptic number.

It is an amenable number.

20642257 is a deficient number, since it is larger than the sum of its proper divisors (1).

20642257 is an equidigital number, since it uses as much as digits as its factorization.

20642257 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6720, while the sum is 28.

The square root of 20642257 is about 4543.3750670619. The cubic root of 20642257 is about 274.3167922039.

Adding to 20642257 its reverse (75224602), we get a palindrome (95866859).

The spelling of 20642257 in words is "twenty million, six hundred forty-two thousand, two hundred fifty-seven".