51661999 has 2 divisors, whose sum is σ = 51662000. Its totient is φ = 51661998.

The previous prime is 51661921. The next prime is 51662011. The reversal of 51661999 is 99916615.

51661999 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 51661999 - 2¹³ = 51653807 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (51661699) 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, 25830999 + 25831000.

It is an arithmetic number, because the mean of its divisors is an integer number (25831000).

Almost surely, 2^51661999 is an apocalyptic number.

51661999 is a deficient number, since it is larger than the sum of its proper divisors (1).

51661999 is an equidigital number, since it uses as much as digits as its factorization.

51661999 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 131220, while the sum is 46.

The square root of 51661999 is about 7187.6281901612. The cubic root of 51661999 is about 372.4406439664.

The spelling of 51661999 in words is "fifty-one million, six hundred sixty-one thousand, nine hundred ninety-nine".