1261998351769 has 9 divisors (see below), whose sum is σ = 1265859953631. Its totient is φ = 1258148504520.

The previous prime is 1261998351623. The next prime is 1261998351793. The reversal of 1261998351769 is 9671538991621.

It is a happy number.

The square root of 1261998351769 is 1123387.

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., 1203327823369 + 58670528400 = 1096963^2 + 242220^2 .

It is not a de Polignac number, because 1261998351769 - 2²⁵ = 1261964797337 is a prime.

It is a super-2 number, since 2×1261998351769² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1261998354769) 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, 412281499 + ... + 412284559.

It is an arithmetic number, because the mean of its divisors is an integer number (140651105959).

Almost surely, 2^{1261998351769} is an apocalyptic number.

1261998351769 is the 1123387-th square number.

1261998351769 is the 561694-th centered octagonal number.

It is an amenable number.

1261998351769 is a deficient number, since it is larger than the sum of its proper divisors (3861601862).

1261998351769 is an frugal number, since it uses more digits than its factorization.

1261998351769 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6856 (or 3428 counting only the distinct ones).

The product of its digits is 44089920, while the sum is 67.

The spelling of 1261998351769 in words is "one trillion, two hundred sixty-one billion, nine hundred ninety-eight million, three hundred fifty-one thousand, seven hundred sixty-nine".