1221001987 has 2 divisors, whose sum is σ = 1221001988. Its totient is φ = 1221001986.

The previous prime is 1221001979. The next prime is 1221002009. The reversal of 1221001987 is 7891001221.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1221001987 - 2³ = 1221001979 is a prime.

It is not a weakly prime, because it can be changed into another prime (1221001907) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610500993 + 610500994.

It is an arithmetic number, because the mean of its divisors is an integer number (610500994).

Almost surely, 2^1221001987 is an apocalyptic number.

1221001987 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221001987 is an equidigital number, since it uses as much as digits as its factorization.

1221001987 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2016, while the sum is 31.

The square root of 1221001987 is about 34942.8388514728. The cubic root of 1221001987 is about 1068.8221782153.

The spelling of 1221001987 in words is "one billion, two hundred twenty-one million, one thousand, nine hundred eighty-seven".