1205120821 has 8 divisors (see below), whose sum is σ = 1239042744. Its totient is φ = 1171270080.

The previous prime is 1205120797. The next prime is 1205120827. The reversal of 1205120821 is 1280215021.

It can be written as a sum of positive squares in 4 ways, for example, as 403608100 + 801512721 = 20090^2 + 28311^2 .

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 1205120821 - 2⁹ = 1205120309 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1205120792 and 1205120801.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1205120827) 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, 17511 + ... + 52123.

It is an arithmetic number, because the mean of its divisors is an integer number (154880343).

Almost surely, 2^1205120821 is an apocalyptic number.

It is an amenable number.

1205120821 is a deficient number, since it is larger than the sum of its proper divisors (33921923).

1205120821 is an equidigital number, since it uses as much as digits as its factorization.

1205120821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35591.

The product of its (nonzero) digits is 320, while the sum is 22.

The square root of 1205120821 is about 34714.8501509080. The cubic root of 1205120821 is about 1064.1680030966.

Adding to 1205120821 its reverse (1280215021), we get a palindrome (2485335842).

The spelling of 1205120821 in words is "one billion, two hundred five million, one hundred twenty thousand, eight hundred twenty-one".