1221020001 has 10 divisors (see below), whose sum is σ = 1823992962. Its totient is φ = 814013280.

The previous prime is 1221019979. The next prime is 1221020069. The reversal of 1221020001 is 1000201221.

It can be written as a sum of positive squares in only one way, i.e., 1193771601 + 27248400 = 34551^2 + 5220^2 .

It is not a de Polignac number, because 1221020001 - 2⁶ = 1221019937 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 (1221020701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 7537080 + ... + 7537241.

Almost surely, 2^1221020001 is an apocalyptic number.

It is an amenable number.

1221020001 is a deficient number, since it is larger than the sum of its proper divisors (602972961).

1221020001 is an equidigital number, since it uses as much as digits as its factorization.

1221020001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15074333 (or 15074324 counting only the distinct ones).

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

The square root of 1221020001 is about 34943.0966143529. The cubic root of 1221020001 is about 1068.8274344634.

Adding to 1221020001 its reverse (1000201221), we get a palindrome (2221221222).

The spelling of 1221020001 in words is "one billion, two hundred twenty-one million, twenty thousand, one".