1221000021 has 32 divisors (see below), whose sum is σ = 1969776000. Its totient is φ = 744557184.

The previous prime is 1221000017. The next prime is 1221000029. The reversal of 1221000021 is 1200001221.

It is not a de Polignac number, because 1221000021 - 2² = 1221000017 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a junction number, because it is equal to n+sod(n) for n = 1220999967 and 1221000012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221000029) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 26160 + ... + 55913.

It is an arithmetic number, because the mean of its divisors is an integer number (61555500).

Almost surely, 2^1221000021 is an apocalyptic number.

It is an amenable number.

1221000021 is a deficient number, since it is larger than the sum of its proper divisors (748775979).

1221000021 is a wasteful number, since it uses less digits than its factorization.

1221000021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 82130 (or 82124 counting only the distinct ones).

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

The square root of 1221000021 is about 34942.8107198033. The cubic root of 1221000021 is about 1068.8216045592.

Adding to 1221000021 its reverse (1200001221), we get a palindrome (2421001242).

It can be divided in two parts, 12 and 21000021, that multiplied together give a palindrome (252000252).

The spelling of 1221000021 in words is "one billion, two hundred twenty-one million, twenty-one", and thus it is an aban number.