61857161521 has 9 divisors (see below), whose sum is σ = 62734540971. Its totient is φ = 60991895952.

The previous prime is 61857161519. The next prime is 61857161551. The reversal of 61857161521 is 12516175816.

The square root of 61857161521 is 248711.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 35113138225 + 26744023296 = 187385^2 + 163536^2 .

It is not a de Polignac number, because 61857161521 - 2¹ = 61857161519 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (61857161551) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 18154200 + ... + 18157606.

Almost surely, 2^61857161521 is an apocalyptic number.

61857161521 is the 248711-st square number.

61857161521 is the 124356-th centered octagonal number.

It is an amenable number.

61857161521 is a deficient number, since it is larger than the sum of its proper divisors (877379450).

61857161521 is an frugal number, since it uses more digits than its factorization.

61857161521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6960 (or 3480 counting only the distinct ones).

The product of its digits is 100800, while the sum is 43.

The spelling of 61857161521 in words is "sixty-one billion, eight hundred fifty-seven million, one hundred sixty-one thousand, five hundred twenty-one".