1211542221 has 4 divisors (see below), whose sum is σ = 1615389632. Its totient is φ = 807694812.

The previous prime is 1211542219. The next prime is 1211542259. The reversal of 1211542221 is 1222451121.

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 not a de Polignac number, because 1211542221 - 2¹ = 1211542219 is a prime.

It is a super-2 number, since 2×1211542221² = 2935669106531225682, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1211542291) 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, 201923701 + ... + 201923706.

It is an arithmetic number, because the mean of its divisors is an integer number (403847408).

Almost surely, 2^1211542221 is an apocalyptic number.

It is an amenable number.

1211542221 is a deficient number, since it is larger than the sum of its proper divisors (403847411).

1211542221 is an equidigital number, since it uses as much as digits as its factorization.

1211542221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 403847410.

The product of its digits is 320, while the sum is 21.

The square root of 1211542221 is about 34807.2150710165. The cubic root of 1211542221 is about 1066.0547702206.

Adding to 1211542221 its reverse (1222451121), we get a palindrome (2433993342).

The spelling of 1211542221 in words is "one billion, two hundred eleven million, five hundred forty-two thousand, two hundred twenty-one".