1221111491 has 2 divisors, whose sum is σ = 1221111492. Its totient is φ = 1221111490.

The previous prime is 1221111461. The next prime is 1221111511. The reversal of 1221111491 is 1941111221.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1221111491 - 2⁶ = 1221111427 is a prime.

It is a super-2 number, since 2×1221111491² = 2982226546904486162, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1221111431) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610555745 + 610555746.

It is an arithmetic number, because the mean of its divisors is an integer number (610555746).

Almost surely, 2^1221111491 is an apocalyptic number.

1221111491 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221111491 is an equidigital number, since it uses as much as digits as its factorization.

1221111491 is an evil number, because the sum of its binary digits is even.

The product of its digits is 144, while the sum is 23.

The square root of 1221111491 is about 34944.4057182262. The cubic root of 1221111491 is about 1068.8541292430.

The spelling of 1221111491 in words is "one billion, two hundred twenty-one million, one hundred eleven thousand, four hundred ninety-one".