1221000020001 has 20 divisors (see below), whose sum is σ = 1826633592432. Its totient is φ = 812808175608.

The previous prime is 1221000019991. The next prime is 1221000020011. The reversal of 1221000020001 is 1000200001221.

It is an interprime number because it is at equal distance from previous prime (1221000019991) and next prime (1221000020011).

It is not a de Polignac number, because 1221000020001 - 2⁶ = 1221000019937 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 (1221000020011) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 10979871 + ... + 11090516.

Almost surely, 2^{1221000020001} is an apocalyptic number.

It is an amenable number.

1221000020001 is a deficient number, since it is larger than the sum of its proper divisors (605633572431).

1221000020001 is an equidigital number, since it uses as much as digits as its factorization.

1221000020001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22071082 (or 22071073 counting only the distinct ones).

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

Adding to 1221000020001 its reverse (1000200001221), we get a palindrome (2221200021222).

The spelling of 1221000020001 in words is "one trillion, two hundred twenty-one billion, twenty thousand, one".