1285645721681 has 4 divisors (see below), whose sum is σ = 1353311286000. Its totient is φ = 1217980157364.

The previous prime is 1285645721669. The next prime is 1285645721707. The reversal of 1285645721681 is 1861275465821.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1285645721681 - 2³⁰ = 1284571979857 is a prime.

It is a super-2 number, since 2×1285645721681² (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 (1285645721611) 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 3 ways as a sum of consecutive naturals, for example, 33832782131 + ... + 33832782168.

It is an arithmetic number, because the mean of its divisors is an integer number (338327821500).

Almost surely, 2^{1285645721681} is an apocalyptic number.

It is an amenable number.

1285645721681 is a deficient number, since it is larger than the sum of its proper divisors (67665564319).

1285645721681 is an equidigital number, since it uses as much as digits as its factorization.

1285645721681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 67665564318.

The product of its digits is 6451200, while the sum is 56.

The spelling of 1285645721681 in words is "one trillion, two hundred eighty-five billion, six hundred forty-five million, seven hundred twenty-one thousand, six hundred eighty-one".