1281664661821 has 8 divisors (see below), whose sum is σ = 1282066070400. Its totient is φ = 1281263327232.

The previous prime is 1281664661803. The next prime is 1281664661839.

1281664661821 is nontrivially palindromic in base 10.

It is an interprime number because it is at equal distance from previous prime (1281664661803) and next prime (1281664661839).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1281664661821 - 2⁹ = 1281664661309 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1281664662821) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 62819580 + ... + 62839978.

It is an arithmetic number, because the mean of its divisors is an integer number (160258258800).

Almost surely, 2^{1281664661821} is an apocalyptic number.

It is an amenable number.

1281664661821 is a deficient number, since it is larger than the sum of its proper divisors (401408579).

1281664661821 is a wasteful number, since it uses less digits than its factorization.

1281664661821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36995.

The product of its digits is 1327104, while the sum is 52.

The spelling of 1281664661821 in words is "one trillion, two hundred eighty-one billion, six hundred sixty-four million, six hundred sixty-one thousand, eight hundred twenty-one".