1221002100021 has 16 divisors (see below), whose sum is σ = 1853220579840. Its totient is φ = 707827303920.

The previous prime is 1221002099987. The next prime is 1221002100029. The reversal of 1221002100021 is 1200012001221.

It is not a de Polignac number, because 1221002100021 - 2⁷ = 1221002099893 is a prime.

It is a super-2 number, since 2×1221002100021² (a number of 25 digits) contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221002100029) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 804348451 + ... + 804349968.

It is an arithmetic number, because the mean of its divisors is an integer number (115826286240).

Almost surely, 2^{1221002100021} is an apocalyptic number.

1221002100021 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1221002100021 is a deficient number, since it is larger than the sum of its proper divisors (632218479819).

1221002100021 is a wasteful number, since it uses less digits than its factorization.

1221002100021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1608698456.

The product of its (nonzero) digits is 16, while the sum is 12.

Adding to 1221002100021 its reverse (1200012001221), we get a palindrome (2421014101242).

The spelling of 1221002100021 in words is "one trillion, two hundred twenty-one billion, two million, one hundred thousand, twenty-one".