1221002011021 has 16 divisors (see below), whose sum is σ = 1318864100400. Its totient is φ = 1123707184128.

The previous prime is 1221002010979. The next prime is 1221002011063. The reversal of 1221002011021 is 1201102001221.

It is an interprime number because it is at equal distance from previous prime (1221002010979) and next prime (1221002011063).

It can be written as a sum of positive squares in 8 ways, for example, as 265906266921 + 955095744100 = 515661^2 + 977290^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221002011021 - 2²¹ = 1220999913869 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (13).

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1221002010992 and 1221002011010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221002011321) 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, 6370375 + ... + 6559243.

It is an arithmetic number, because the mean of its divisors is an integer number (82429006275).

Almost surely, 2^{1221002011021} is an apocalyptic number.

It is an amenable number.

1221002011021 is a deficient number, since it is larger than the sum of its proper divisors (97862089379).

1221002011021 is a wasteful number, since it uses less digits than its factorization.

1221002011021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 190368.

The product of its (nonzero) digits is 16, while the sum is 13.

Adding to 1221002011021 its reverse (1201102001221), we get a palindrome (2422104012242).

The spelling of 1221002011021 in words is "one trillion, two hundred twenty-one billion, two million, eleven thousand, twenty-one".