20638557 has 20 divisors (see below), whose sum is σ = 31343356. Its totient is φ = 13530240.

The previous prime is 20638523. The next prime is 20638559. The reversal of 20638557 is 75583602.

It can be written as a sum of positive squares in 2 ways, for example, as 9308601 + 11329956 = 3051^2 + 3366^2 .

It is not a de Polignac number, because 20638557 - 2⁸ = 20638301 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20638559) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 2853 + ... + 7029.

Almost surely, 2^20638557 is an apocalyptic number.

20638557 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

20638557 is a deficient number, since it is larger than the sum of its proper divisors (10704799).

20638557 is an equidigital number, since it uses as much as digits as its factorization.

20638557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4250 (or 4241 counting only the distinct ones).

The product of its (nonzero) digits is 50400, while the sum is 36.

The square root of 20638557 is about 4542.9678625322. The cubic root of 20638557 is about 274.3004013480.

The spelling of 20638557 in words is "twenty million, six hundred thirty-eight thousand, five hundred fifty-seven".