20139661 has 2 divisors, whose sum is σ = 20139662. Its totient is φ = 20139660.

The previous prime is 20139643. The next prime is 20139673. The reversal of 20139661 is 16693102.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17690436 + 2449225 = 4206^2 + 1565^2 .

It is a cyclic number.

It is not a de Polignac number, because 20139661 - 2¹⁵ = 20106893 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20137661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10069830 + 10069831.

It is an arithmetic number, because the mean of its divisors is an integer number (10069831).

Almost surely, 2^20139661 is an apocalyptic number.

It is an amenable number.

20139661 is a deficient number, since it is larger than the sum of its proper divisors (1).

20139661 is an equidigital number, since it uses as much as digits as its factorization.

20139661 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1944, while the sum is 28.

The square root of 20139661 is about 4487.7233649146. The cubic root of 20139661 is about 272.0721271020.

The spelling of 20139661 in words is "twenty million, one hundred thirty-nine thousand, six hundred sixty-one".