1988561 has 2 divisors, whose sum is σ = 1988562. Its totient is φ = 1988560.

The previous prime is 1988551. The next prime is 1988563. The reversal of 1988561 is 1658891.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1960000 + 28561 = 1400^2 + 169^2 .

It is a cyclic number.

It is not a de Polignac number, because 1988561 - 2¹⁰ = 1987537 is a prime.

Together with 1988563, it forms a pair of twin primes.

It is a Chen prime.

It is an Ulam number.

It is not a weakly prime, because it can be changed into another prime (1988563) 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, 994280 + 994281.

It is an arithmetic number, because the mean of its divisors is an integer number (994281).

2^1988561 is an apocalyptic number.

It is an amenable number.

1988561 is a deficient number, since it is larger than the sum of its proper divisors (1).

1988561 is an equidigital number, since it uses as much as digits as its factorization.

1988561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 17280, while the sum is 38.

The square root of 1988561 is about 1410.1634657018. The cubic root of 1988561 is about 125.7514416318.

The spelling of 1988561 in words is "one million, nine hundred eighty-eight thousand, five hundred sixty-one".