1221311091 has 32 divisors (see below), whose sum is σ = 2186408448. Its totient is φ = 585642240.

The previous prime is 1221311081. The next prime is 1221311107. The reversal of 1221311091 is 1901131221.

It is a happy number.

It is not a de Polignac number, because 1221311091 - 2⁷ = 1221310963 is a prime.

It is a super-2 number, since 2×1221311091² = 2983201561999220562, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is not an unprimeable number, because it can be changed into a prime (1221311071) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 200346 + ... + 206351.

It is an arithmetic number, because the mean of its divisors is an integer number (68325264).

Almost surely, 2^1221311091 is an apocalyptic number.

1221311091 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1221311091 is a deficient number, since it is larger than the sum of its proper divisors (965097357).

1221311091 is a wasteful number, since it uses less digits than its factorization.

1221311091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 406731.

The product of its (nonzero) digits is 108, while the sum is 21.

The square root of 1221311091 is about 34947.2615665377. The cubic root of 1221311091 is about 1068.9123635273.

The spelling of 1221311091 in words is "one billion, two hundred twenty-one million, three hundred eleven thousand, ninety-one".