1290001661 has 16 divisors (see below), whose sum is σ = 1405425840. Its totient is φ = 1176975360.

The previous prime is 1290001649. The next prime is 1290001663. The reversal of 1290001661 is 1661000921.

It can be written as a sum of positive squares in 8 ways, for example, as 17724100 + 1272277561 = 4210^2 + 35669^2 .

It is a cyclic number.

It is not a de Polignac number, because 1290001661 - 2⁶ = 1290001597 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 1290001661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1290001663) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 405485 + ... + 408653.

It is an arithmetic number, because the mean of its divisors is an integer number (87839115).

Almost surely, 2^1290001661 is an apocalyptic number.

It is an amenable number.

1290001661 is a deficient number, since it is larger than the sum of its proper divisors (115424179).

1290001661 is a wasteful number, since it uses less digits than its factorization.

1290001661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3536.

The product of its (nonzero) digits is 648, while the sum is 26.

The square root of 1290001661 is about 35916.5931151606. The cubic root of 1290001661 is about 1088.5877006732.

The spelling of 1290001661 in words is "one billion, two hundred ninety million, one thousand, six hundred sixty-one".