20644157 has 2 divisors, whose sum is σ = 20644158. Its totient is φ = 20644156.

The previous prime is 20644153. The next prime is 20644177. The reversal of 20644157 is 75144602.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14661241 + 5982916 = 3829^2 + 2446^2 .

It is a cyclic number.

It is not a de Polignac number, because 20644157 - 2² = 20644153 is a prime.

It is equal to p_1308818 and since 20644157 and 1308818 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 (20644153) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10322078 + 10322079.

It is an arithmetic number, because the mean of its divisors is an integer number (10322079).

Almost surely, 2^20644157 is an apocalyptic number.

It is an amenable number.

20644157 is a deficient number, since it is larger than the sum of its proper divisors (1).

20644157 is an equidigital number, since it uses as much as digits as its factorization.

20644157 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6720, while the sum is 29.

The square root of 20644157 is about 4543.5841579088. The cubic root of 20644157 is about 274.3252083688.

Adding to 20644157 its reverse (75144602), we get a palindrome (95788759).

The spelling of 20644157 in words is "twenty million, six hundred forty-four thousand, one hundred fifty-seven".