1281285899721 has 45 divisors (see below), whose sum is σ = 1927799039991. Its totient is φ = 848084920848.

The previous prime is 1281285899701. The next prime is 1281285899749. The reversal of 1281285899721 is 1279985821821.

The square root of 1281285899721 is 1131939.

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

1281285899721 is a `hidden beast` number, since 1 + 2 + 8 + 1 + 28 + 589 + 9 + 7 + 21 = 666.

It can be written as a sum of positive squares in only one way, i.e., 1165525364025 + 115760535696 = 1079595^2 + 340236^2 .

It is not a de Polignac number, because 1281285899721 - 2⁵ = 1281285899689 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1281285899701) 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 44 ways as a sum of consecutive naturals, for example, 1762428660 + ... + 1762429386.

Almost surely, 2^{1281285899721} is an apocalyptic number.

1281285899721 is the 1131939-th square number.

1281285899721 is the 565970-th centered octagonal number.

It is an amenable number.

1281285899721 is a deficient number, since it is larger than the sum of its proper divisors (646513140270).

1281285899721 is an frugal number, since it uses more digits than its factorization.

1281285899721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1812 (or 903 counting only the distinct ones).

The product of its digits is 11612160, while the sum is 63.

The spelling of 1281285899721 in words is "one trillion, two hundred eighty-one billion, two hundred eighty-five million, eight hundred ninety-nine thousand, seven hundred twenty-one".