20661139 has 2 divisors, whose sum is σ = 20661140. Its totient is φ = 20661138.

The previous prime is 20661131. The next prime is 20661143. The reversal of 20661139 is 93116602.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20661139 - 2³ = 20661131 is a prime.

It is not a weakly prime, because it can be changed into another prime (20661131) 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, 10330569 + 10330570.

It is an arithmetic number, because the mean of its divisors is an integer number (10330570).

Almost surely, 2^20661139 is an apocalyptic number.

20661139 is a deficient number, since it is larger than the sum of its proper divisors (1).

20661139 is an equidigital number, since it uses as much as digits as its factorization.

20661139 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 20661139 is about 4545.4525627268. The cubic root of 20661139 is about 274.4004082406.

The spelling of 20661139 in words is "twenty million, six hundred sixty-one thousand, one hundred thirty-nine".