1221121811 has 32 divisors (see below), whose sum is σ = 1593715200. Its totient is φ = 908547840.

The previous prime is 1221121793. The next prime is 1221121831. The reversal of 1221121811 is 1181211221.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 1221121811 - 2¹⁸ = 1220859667 is a prime.

It is a super-2 number, since 2×1221121811² = 2982276954599839442, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (1221121831) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 237791 + ... + 242871.

It is an arithmetic number, because the mean of its divisors is an integer number (49803600).

Almost surely, 2^1221121811 is an apocalyptic number.

1221121811 is a deficient number, since it is larger than the sum of its proper divisors (372593389).

1221121811 is a wasteful number, since it uses less digits than its factorization.

1221121811 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5259.

The product of its digits is 64, while the sum is 20.

The square root of 1221121811 is about 34944.5533810349. The cubic root of 1221121811 is about 1068.8571403095.

The spelling of 1221121811 in words is "one billion, two hundred twenty-one million, one hundred twenty-one thousand, eight hundred eleven".