1216809754281 has 27 divisors (see below), whose sum is σ = 1931980721853. Its totient is φ = 737438395320.

The previous prime is 1216809754261. The next prime is 1216809754291. The reversal of 1216809754281 is 1824579086121.

The square root of 1216809754281 is 1103091.

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

1216809754281 is a `hidden beast` number, since 1 + 2 + 1 + 6 + 8 + 0 + 97 + 542 + 8 + 1 = 666.

It is not a de Polignac number, because 1216809754281 - 2¹⁵ = 1216809721513 is a prime.

It is a super-2 number, since 2×1216809754281² (a number of 25 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (1216809754261) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 36385290 + ... + 36418716.

Almost surely, 2^{1216809754281} is an apocalyptic number.

1216809754281 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1216809754281 is the 1103091-st square number.

1216809754281 is the 551546-th centered octagonal number.

It is an amenable number.

1216809754281 is a deficient number, since it is larger than the sum of its proper divisors (715170967572).

1216809754281 is an frugal number, since it uses more digits than its factorization.

1216809754281 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 66882 (or 33441 counting only the distinct ones).

The product of its (nonzero) digits is 1935360, while the sum is 54.

The spelling of 1216809754281 in words is "one trillion, two hundred sixteen billion, eight hundred nine million, seven hundred fifty-four thousand, two hundred eighty-one".