1691531 has 2 divisors, whose sum is σ = 1691532. Its totient is φ = 1691530.

The previous prime is 1691527. The next prime is 1691533. The reversal of 1691531 is 1351961.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1691531 - 2² = 1691527 is a prime.

It is a super-2 number, since 2×1691531² = 5722554247922, which contains 22 as substring.

Together with 1691533, it forms a pair of twin primes.

It is a Chen prime.

It is an Ulam number.

It is equal to p₁₂₇₅₃₈ and since 1691531 and 127538 have the same sum of digits, it is a Honaker prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1691531.

It is not a weakly prime, because it can be changed into another prime (1691533) 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, 845765 + 845766.

It is an arithmetic number, because the mean of its divisors is an integer number (845766).

2^1691531 is an apocalyptic number.

1691531 is a deficient number, since it is larger than the sum of its proper divisors (1).

1691531 is an equidigital number, since it uses as much as digits as its factorization.

1691531 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 810, while the sum is 26.

The square root of 1691531 is about 1300.5887128528. The cubic root of 1691531 is about 119.1498007547.

It can be divided in two parts, 1691 and 531, that added together give a palindrome (2222).

The spelling of 1691531 in words is "one million, six hundred ninety-one thousand, five hundred thirty-one".