1661051621 has 2 divisors, whose sum is σ = 1661051622. Its totient is φ = 1661051620.

The previous prime is 1661051537. The next prime is 1661051633. The reversal of 1661051621 is 1261501661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1278849121 + 382202500 = 35761^2 + 19550^2 .

It is a cyclic number.

It is not a de Polignac number, because 1661051621 - 2¹⁰ = 1661050597 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1661051671) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 830525810 + 830525811.

It is an arithmetic number, because the mean of its divisors is an integer number (830525811).

Almost surely, 2^1661051621 is an apocalyptic number.

It is an amenable number.

1661051621 is a deficient number, since it is larger than the sum of its proper divisors (1).

1661051621 is an equidigital number, since it uses as much as digits as its factorization.

1661051621 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2160, while the sum is 29.

The square root of 1661051621 is about 40756.0010427912. The cubic root of 1661051621 is about 1184.2981288779.

The spelling of 1661051621 in words is "one billion, six hundred sixty-one million, fifty-one thousand, six hundred twenty-one".