1891989009 has 33 divisors (see below), whose sum is σ = 2853910633. Its totient is φ = 1254279492.

The previous prime is 1891988999. The next prime is 1891989031. The reversal of 1891989009 is 9009891981.

The square root of 1891989009 is 43497.

It is a perfect power (a square), and thus also a powerful number.

It is not a de Polignac number, because 1891989009 - 2⁷ = 1891988881 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1891989059) by changing a digit.

It is a polite number, since it can be written in 32 ways as a sum of consecutive naturals, for example, 10569682 + ... + 10569860.

Almost surely, 2^1891989009 is an apocalyptic number.

1891989009 is the 43497-th square number.

1891989009 is the 21749-th centered octagonal number.

It is an amenable number.

1891989009 is a deficient number, since it is larger than the sum of its proper divisors (961921624).

1891989009 is an frugal number, since it uses more digits than its factorization.

1891989009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 388 (or 182 counting only the distinct ones).

The product of its (nonzero) digits is 419904, while the sum is 54.

The cubic root of 1891989009 is about 1236.8191560626.

Multiplying 1891989009 by its product of nonzero digits (419904), we get a square (794453752835136 = 28186056²).

The spelling of 1891989009 in words is "one billion, eight hundred ninety-one million, nine hundred eighty-nine thousand, nine".