1281121021 has 4 divisors (see below), whose sum is σ = 1286481600. Its totient is φ = 1275760444.

The previous prime is 1281121007. The next prime is 1281121027. The reversal of 1281121021 is 1201211821.

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 1281121021 - 2⁵ = 1281120989 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1281121021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1281121027) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2679931 + ... + 2680408.

It is an arithmetic number, because the mean of its divisors is an integer number (321620400).

Almost surely, 2^1281121021 is an apocalyptic number.

It is an amenable number.

1281121021 is a deficient number, since it is larger than the sum of its proper divisors (5360579).

1281121021 is an equidigital number, since it uses as much as digits as its factorization.

1281121021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5360578.

The product of its (nonzero) digits is 64, while the sum is 19.

The square root of 1281121021 is about 35792.7509560246. The cubic root of 1281121021 is about 1086.0839248938.

Adding to 1281121021 its reverse (1201211821), we get a palindrome (2482332842).

The spelling of 1281121021 in words is "one billion, two hundred eighty-one million, one hundred twenty-one thousand, twenty-one".