1211225821 has 16 divisors (see below), whose sum is σ = 1361645488. Its totient is φ = 1069977600.

The previous prime is 1211225773. The next prime is 1211225857. The reversal of 1211225821 is 1285221121.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 108056025 + 1103169796 = 10395^2 + 33214^2 .

It is a cyclic number.

It is not a de Polignac number, because 1211225821 - 2²⁹ = 674354909 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1211225921) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8701 + ... + 49981.

It is an arithmetic number, because the mean of its divisors is an integer number (85102843).

Almost surely, 2^1211225821 is an apocalyptic number.

It is an amenable number.

1211225821 is a deficient number, since it is larger than the sum of its proper divisors (150419667).

1211225821 is a wasteful number, since it uses less digits than its factorization.

1211225821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41392.

The product of its digits is 640, while the sum is 25.

The square root of 1211225821 is about 34802.6697395473. The cubic root of 1211225821 is about 1065.9619603870.

Adding to 1211225821 its reverse (1285221121), we get a palindrome (2496446942).

The spelling of 1211225821 in words is "one billion, two hundred eleven million, two hundred twenty-five thousand, eight hundred twenty-one".