1221011001 has 12 divisors (see below), whose sum is σ = 2015637312. Its totient is φ = 697720536.

The previous prime is 1221010997. The next prime is 1221011021. The reversal of 1221011001 is 1001101221.

It is a happy number.

It is not a de Polignac number, because 1221011001 - 2² = 1221010997 is a prime.

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

It is not an unprimeable number, because it can be changed into a prime (1221011021) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 9690501 + ... + 9690626.

It is an arithmetic number, because the mean of its divisors is an integer number (167969776).

Almost surely, 2^1221011001 is an apocalyptic number.

It is an amenable number.

1221011001 is a deficient number, since it is larger than the sum of its proper divisors (794626311).

1221011001 is a wasteful number, since it uses less digits than its factorization.

1221011001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19381140 (or 19381137 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 9.

The square root of 1221011001 is about 34942.9678333138. The cubic root of 1221011001 is about 1068.8248083883.

Adding to 1221011001 its reverse (1001101221), we get a palindrome (2222112222).

The spelling of 1221011001 in words is "one billion, two hundred twenty-one million, eleven thousand, one".