1651681 has 2 divisors, whose sum is σ = 1651682. Its totient is φ = 1651680.

The previous prime is 1651667. The next prime is 1651691. The reversal of 1651681 is 1861561.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1648656 + 3025 = 1284^2 + 55^2 .

It is a cyclic number.

It is not a de Polignac number, because 1651681 - 2⁷ = 1651553 is a prime.

It is a super-2 number, since 2×1651681² = 5456100251522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1651621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 825840 + 825841.

It is an arithmetic number, because the mean of its divisors is an integer number (825841).

2^1651681 is an apocalyptic number.

It is an amenable number.

1651681 is a deficient number, since it is larger than the sum of its proper divisors (1).

1651681 is an equidigital number, since it uses as much as digits as its factorization.

1651681 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1440, while the sum is 28.

The square root of 1651681 is about 1285.1774196585. The cubic root of 1651681 is about 118.2066903183.

Subtracting from 1651681 its sum of digits (28), we obtain a triangular number (1651653 = T₁₈₁₇).

It can be divided in two parts, 1651 and 681, that added together give a palindrome (2332).

The spelling of 1651681 in words is "one million, six hundred fifty-one thousand, six hundred eighty-one".