1221000020 has 12 divisors (see below), whose sum is σ = 2564100084. Its totient is φ = 488400000.

The previous prime is 1221000017. The next prime is 1221000029. The reversal of 1221000020 is 200001221.

It can be written as a sum of positive squares in 2 ways, for example, as 679227844 + 541772176 = 26062^2 + 23276^2 .

It is a junction number, because it is equal to n+sod(n) for n = 1220999971 and 1221000007.

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 polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 30524981 + ... + 30525020.

It is an arithmetic number, because the mean of its divisors is an integer number (213675007).

Almost surely, 2^1221000020 is an apocalyptic number.

1221000020 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1221000020 is an abundant number, since it is smaller than the sum of its proper divisors (1343100064).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1221000020 is a wasteful number, since it uses less digits than its factorization.

1221000020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 61050010 (or 61050008 counting only the distinct ones).

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

The square root of 1221000020 is about 34942.8107054942. The cubic root of 1221000020 is about 1068.8216042674.

Adding to 1221000020 its reverse (200001221), we get a palindrome (1421001241).

The spelling of 1221000020 in words is "one billion, two hundred twenty-one million, twenty", and thus it is an aban number.