20188261 has 2 divisors, whose sum is σ = 20188262. Its totient is φ = 20188260.

The previous prime is 20188249. The next prime is 20188291. The reversal of 20188261 is 16288102.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20079361 + 108900 = 4481^2 + 330^2 .

It is a cyclic number.

It is not a de Polignac number, because 20188261 - 2¹¹ = 20186213 is a prime.

It is equal to p_1281835 and since 20188261 and 1281835 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 (20188291) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10094130 + 10094131.

It is an arithmetic number, because the mean of its divisors is an integer number (10094131).

Almost surely, 2^20188261 is an apocalyptic number.

It is an amenable number.

20188261 is a deficient number, since it is larger than the sum of its proper divisors (1).

20188261 is an equidigital number, since it uses as much as digits as its factorization.

20188261 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1536, while the sum is 28.

The square root of 20188261 is about 4493.1348744501. The cubic root of 20188261 is about 272.2908014794.

It can be divided in two parts, 20188 and 261, that added together give a square (20449 = 143²).

The spelling of 20188261 in words is "twenty million, one hundred eighty-eight thousand, two hundred sixty-one".