1691988 has 48 divisors (see below), whose sum is σ = 4280640. Its totient is φ = 518400.

The previous prime is 1691983. The next prime is 1692013. The reversal of 1691988 is 8891961.

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1691983) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9258 + ... + 9438.

It is an arithmetic number, because the mean of its divisors is an integer number (89180).

2^1691988 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1691988, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2140320).

1691988 is an abundant number, since it is smaller than the sum of its proper divisors (2588652).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1691988 is a wasteful number, since it uses less digits than its factorization.

1691988 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 248 (or 246 counting only the distinct ones).

The product of its digits is 31104, while the sum is 42.

The square root of 1691988 is about 1300.7643906565. The cubic root of 1691988 is about 119.1605300006.

The spelling of 1691988 in words is "one million, six hundred ninety-one thousand, nine hundred eighty-eight".