1212220021 has 4 divisors (see below), whose sum is σ = 1212446592. Its totient is φ = 1211993452.

The previous prime is 1212219989. The next prime is 1212220033. The reversal of 1212220021 is 1200222121.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1212220021 - 2⁵ = 1212219989 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1212219983 and 1212220010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1212220091) 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, 105061 + ... + 116026.

It is an arithmetic number, because the mean of its divisors is an integer number (303111648).

Almost surely, 2^1212220021 is an apocalyptic number.

It is an amenable number.

1212220021 is a deficient number, since it is larger than the sum of its proper divisors (226571).

1212220021 is an equidigital number, since it uses as much as digits as its factorization.

1212220021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 226570.

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

The square root of 1212220021 is about 34816.9501967074. The cubic root of 1212220021 is about 1066.2535353990.

Adding to 1212220021 its reverse (1200222121), we get a palindrome (2412442142).

The spelling of 1212220021 in words is "one billion, two hundred twelve million, two hundred twenty thousand, twenty-one".