1646681551 has 2 divisors, whose sum is σ = 1646681552. Its totient is φ = 1646681550.

The previous prime is 1646681507. The next prime is 1646681581. The reversal of 1646681551 is 1551866461.

It is a strong prime.

It is an emirp because it is prime and its reverse (1551866461) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1646681551 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1646681498 and 1646681507.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1646681581) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 823340775 + 823340776.

It is an arithmetic number, because the mean of its divisors is an integer number (823340776).

Almost surely, 2^1646681551 is an apocalyptic number.

1646681551 is a deficient number, since it is larger than the sum of its proper divisors (1).

1646681551 is an equidigital number, since it uses as much as digits as its factorization.

1646681551 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 172800, while the sum is 43.

The square root of 1646681551 is about 40579.3241811640. The cubic root of 1646681551 is about 1180.8730374811.

The spelling of 1646681551 in words is "one billion, six hundred forty-six million, six hundred eighty-one thousand, five hundred fifty-one".