1691561 has 2 divisors, whose sum is σ = 1691562. Its totient is φ = 1691560.

The previous prime is 1691533. The next prime is 1691567. The reversal of 1691561 is 1651961.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1081600 + 609961 = 1040^2 + 781^2 .

It is an emirp because it is prime and its reverse (1651961) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1691561 - 2¹⁰ = 1690537 is a prime.

It is a super-2 number, since 2×1691561² = 5722757233442, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (1691567) 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, 845780 + 845781.

It is an arithmetic number, because the mean of its divisors is an integer number (845781).

2^1691561 is an apocalyptic number.

It is an amenable number.

1691561 is a deficient number, since it is larger than the sum of its proper divisors (1).

1691561 is an equidigital number, since it uses as much as digits as its factorization.

1691561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1620, while the sum is 29.

The square root of 1691561 is about 1300.6002460403. The cubic root of 1691561 is about 119.1505051409.

The spelling of 1691561 in words is "one million, six hundred ninety-one thousand, five hundred sixty-one".