1661841989 has 2 divisors, whose sum is σ = 1661841990. Its totient is φ = 1661841988.

The previous prime is 1661841959. The next prime is 1661842001. The reversal of 1661841989 is 9891481661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1597361089 + 64480900 = 39967^2 + 8030^2 .

It is a cyclic number.

It is not a de Polignac number, because 1661841989 - 2²⁸ = 1393406533 is a prime.

It is a super-2 number, since 2×1661841989² = 5523437592806952242, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 1661841989.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1661841959) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 830920994 + 830920995.

It is an arithmetic number, because the mean of its divisors is an integer number (830920995).

Almost surely, 2^1661841989 is an apocalyptic number.

It is an amenable number.

1661841989 is a deficient number, since it is larger than the sum of its proper divisors (1).

1661841989 is an equidigital number, since it uses as much as digits as its factorization.

1661841989 is an evil number, because the sum of its binary digits is even.

The product of its digits is 746496, while the sum is 53.

The square root of 1661841989 is about 40765.6962285694. The cubic root of 1661841989 is about 1184.4859381968.

The spelling of 1661841989 in words is "one billion, six hundred sixty-one million, eight hundred forty-one thousand, nine hundred eighty-nine".