1221002001 has 12 divisors (see below), whose sum is σ = 1764051328. Its totient is φ = 813825144.

The previous prime is 1221001987. The next prime is 1221002009. The reversal of 1221002001 is 1002001221.

It is not a de Polignac number, because 1221002001 - 2¹¹ = 1220999953 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1221002009) 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 in 11 ways as a sum of consecutive naturals, for example, 39876 + ... + 63498.

Almost surely, 2^1221002001 is an apocalyptic number.

It is an amenable number.

1221002001 is a deficient number, since it is larger than the sum of its proper divisors (543049327).

1221002001 is a wasteful number, since it uses less digits than its factorization.

1221002001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29372 (or 29369 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

The square root of 1221002001 is about 34942.8390518000. The cubic root of 1221002001 is about 1068.8221823003.

Adding to 1221002001 its reverse (1002001221), we get a palindrome (2223003222).

The spelling of 1221002001 in words is "one billion, two hundred twenty-one million, two thousand, one".