1661989799 has 2 divisors, whose sum is σ = 1661989800. Its totient is φ = 1661989798.

The previous prime is 1661989781. The next prime is 1661989811. The reversal of 1661989799 is 9979891661.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1661989799 - 2¹⁶ = 1661924263 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1661989709) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 830994899 + 830994900.

It is an arithmetic number, because the mean of its divisors is an integer number (830994900).

Almost surely, 2^1661989799 is an apocalyptic number.

1661989799 is a deficient number, since it is larger than the sum of its proper divisors (1).

1661989799 is an equidigital number, since it uses as much as digits as its factorization.

1661989799 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 13226976, while the sum is 65.

The square root of 1661989799 is about 40767.5091095838. The cubic root of 1661989799 is about 1184.5210545872.

The spelling of 1661989799 in words is "one billion, six hundred sixty-one million, nine hundred eighty-nine thousand, seven hundred ninety-nine".