1221202021 has 32 divisors (see below), whose sum is σ = 1439399808. Its totient is φ = 1025740800.

The previous prime is 1221202013. The next prime is 1221202027. The reversal of 1221202021 is 1202021221.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 1221202021 - 2³ = 1221202013 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 = 1221201992 and 1221202010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221202027) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1016221 + ... + 1017421.

It is an arithmetic number, because the mean of its divisors is an integer number (44981244).

Almost surely, 2^1221202021 is an apocalyptic number.

It is an amenable number.

1221202021 is a deficient number, since it is larger than the sum of its proper divisors (218197787).

1221202021 is a wasteful number, since it uses less digits than its factorization.

1221202021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1381.

The product of its (nonzero) digits is 32, while the sum is 13.

The square root of 1221202021 is about 34945.7010374667. The cubic root of 1221202021 is about 1068.8805426033.

Adding to 1221202021 its reverse (1202021221), we get a palindrome (2423223242).

The spelling of 1221202021 in words is "one billion, two hundred twenty-one million, two hundred two thousand, twenty-one".