1305121021 has 4 divisors (see below), whose sum is σ = 1305322432. Its totient is φ = 1304919612.

The previous prime is 1305120997. The next prime is 1305121043. The reversal of 1305121021 is 1201215031.

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 1305121021 - 2¹³ = 1305112829 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1305120986 and 1305121004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1305121121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 90651 + ... + 104056.

It is an arithmetic number, because the mean of its divisors is an integer number (326330608).

Almost surely, 2^1305121021 is an apocalyptic number.

It is an amenable number.

1305121021 is a deficient number, since it is larger than the sum of its proper divisors (201411).

1305121021 is an equidigital number, since it uses as much as digits as its factorization.

1305121021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 201410.

The product of its (nonzero) digits is 60, while the sum is 16.

The square root of 1305121021 is about 36126.4587387139. The cubic root of 1305121021 is about 1092.8240940906.

Adding to 1305121021 its reverse (1201215031), we get a palindrome (2506336052).

The spelling of 1305121021 in words is "one billion, three hundred five million, one hundred twenty-one thousand, twenty-one".