1691391 has 16 divisors (see below), whose sum is σ = 2508800. Its totient is φ = 1006560.

The previous prime is 1691387. The next prime is 1691401. The reversal of 1691391 is 1931961.

It is not a de Polignac number, because 1691391 - 2² = 1691387 is a prime.

It is a Duffinian number.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1691321) 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, 510 + ... + 1908.

It is an arithmetic number, because the mean of its divisors is an integer number (156800).

2^1691391 is an apocalyptic number.

1691391 is a deficient number, since it is larger than the sum of its proper divisors (817409).

1691391 is a wasteful number, since it uses less digits than its factorization.

1691391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1446.

The product of its digits is 1458, while the sum is 30.

The square root of 1691391 is about 1300.5348899587. The cubic root of 1691391 is about 119.1465135094.

The spelling of 1691391 in words is "one million, six hundred ninety-one thousand, three hundred ninety-one".