1661281057 has 2 divisors, whose sum is σ = 1661281058. Its totient is φ = 1661281056.

The previous prime is 1661281051. The next prime is 1661281081. The reversal of 1661281057 is 7501821661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 944701696 + 716579361 = 30736^2 + 26769^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1661281057 is a prime.

It is not a weakly prime, because it can be changed into another prime (1661281051) 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, 830640528 + 830640529.

It is an arithmetic number, because the mean of its divisors is an integer number (830640529).

Almost surely, 2^1661281057 is an apocalyptic number.

It is an amenable number.

1661281057 is a deficient number, since it is larger than the sum of its proper divisors (1).

1661281057 is an equidigital number, since it uses as much as digits as its factorization.

1661281057 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 20160, while the sum is 37.

The square root of 1661281057 is about 40758.8156967300. The cubic root of 1661281057 is about 1184.3526541984.

The spelling of 1661281057 in words is "one billion, six hundred sixty-one million, two hundred eighty-one thousand, fifty-seven".