505991791561 has 9 divisors (see below), whose sum is σ = 537519697351. Its totient is φ = 476216187232.

The previous prime is 505991791523. The next prime is 505991791607. The reversal of 505991791561 is 165197199505.

The square root of 505991791561 is 711331.

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., 393938246025 + 112053545536 = 627645^2 + 334744^2 .

It is not a de Polignac number, because 505991791561 - 2²¹ = 505989694409 is a prime.

It is a super-2 number, since 2×505991791561² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 505991791496 and 505991791505.

It is not an unprimeable number, because it can be changed into a prime (505991491561) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 12071706 + ... + 12113548.

Almost surely, 2^505991791561 is an apocalyptic number.

505991791561 is the 711331-st square number.

505991791561 is the 355666-th centered octagonal number.

It is an amenable number.

505991791561 is a deficient number, since it is larger than the sum of its proper divisors (31527905790).

505991791561 is an frugal number, since it uses more digits than its factorization.

505991791561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83720 (or 41860 counting only the distinct ones).

The product of its (nonzero) digits is 3827250, while the sum is 58.

The spelling of 505991791561 in words is "five hundred five billion, nine hundred ninety-one million, seven hundred ninety-one thousand, five hundred sixty-one".