1211255021 has 4 divisors (see below), whose sum is σ = 1211766972. Its totient is φ = 1210743072.

The previous prime is 1211255009. The next prime is 1211255029. The reversal of 1211255021 is 1205521121.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1205521121 = 7 ⋅172217303.

It can be written as a sum of positive squares in 2 ways, for example, as 605848996 + 605406025 = 24614^2 + 24605^2 .

It is a cyclic number.

It is not a de Polignac number, because 1211255021 - 2²² = 1207060717 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1211254984 and 1211255002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1211255029) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 252410 + ... + 257163.

It is an arithmetic number, because the mean of its divisors is an integer number (302941743).

Almost surely, 2^1211255021 is an apocalyptic number.

It is an amenable number.

1211255021 is a deficient number, since it is larger than the sum of its proper divisors (511951).

1211255021 is an equidigital number, since it uses as much as digits as its factorization.

1211255021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 511950.

The product of its (nonzero) digits is 200, while the sum is 20.

The square root of 1211255021 is about 34803.0892450656. The cubic root of 1211255021 is about 1065.9705263204.

Adding to 1211255021 its reverse (1205521121), we get a palindrome (2416776142).

The spelling of 1211255021 in words is "one billion, two hundred eleven million, two hundred fifty-five thousand, twenty-one".