1961581 has 2 divisors, whose sum is σ = 1961582. Its totient is φ = 1961580.

The previous prime is 1961551. The next prime is 1961593. The reversal of 1961581 is 1851691.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1876900 + 84681 = 1370^2 + 291^2 .

It is a cyclic number.

It is not a de Polignac number, because 1961581 - 2⁵ = 1961549 is a prime.

It is a super-2 number, since 2×1961581² = 7695600039122, which contains 22 as substring.

1961581 is a lucky number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1961501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 980790 + 980791.

It is an arithmetic number, because the mean of its divisors is an integer number (980791).

2^1961581 is an apocalyptic number.

It is an amenable number.

1961581 is a deficient number, since it is larger than the sum of its proper divisors (1).

1961581 is an equidigital number, since it uses as much as digits as its factorization.

1961581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2160, while the sum is 31.

The square root of 1961581 is about 1400.5645290382. The cubic root of 1961581 is about 125.1801349532.

The spelling of 1961581 in words is "one million, nine hundred sixty-one thousand, five hundred eighty-one".