1221131987 has 4 divisors (see below), whose sum is σ = 1250915736. Its totient is φ = 1191348240.

The previous prime is 1221131963. The next prime is 1221131999. The reversal of 1221131987 is 7891311221.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 7891311221 = 3943 ⋅2001347.

It is a cyclic number.

It is not a de Polignac number, because 1221131987 - 2²⁴ = 1204354771 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1221131917) 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 3 ways as a sum of consecutive naturals, for example, 14891813 + ... + 14891894.

It is an arithmetic number, because the mean of its divisors is an integer number (312728934).

Almost surely, 2^1221131987 is an apocalyptic number.

1221131987 is a deficient number, since it is larger than the sum of its proper divisors (29783749).

1221131987 is an equidigital number, since it uses as much as digits as its factorization.

1221131987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29783748.

The product of its digits is 6048, while the sum is 35.

The square root of 1221131987 is about 34944.6989828214. The cubic root of 1221131987 is about 1068.8601093444.

The spelling of 1221131987 in words is "one billion, two hundred twenty-one million, one hundred thirty-one thousand, nine hundred eighty-seven".