1221020099 has 8 divisors (see below), whose sum is σ = 1322727840. Its totient is φ = 1127093448.

The previous prime is 1221020093. The next prime is 1221020111. The reversal of 1221020099 is 9900201221.

It is a happy number.

It is not a de Polignac number, because 1221020099 - 2²⁸ = 952584643 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1221020093) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 275687 + ... + 280080.

It is an arithmetic number, because the mean of its divisors is an integer number (165340980).

Almost surely, 2^1221020099 is an apocalyptic number.

1221020099 is a deficient number, since it is larger than the sum of its proper divisors (101707741).

1221020099 is an frugal number, since it uses more digits than its factorization.

1221020099 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 555806 (or 555780 counting only the distinct ones).

The product of its (nonzero) digits is 648, while the sum is 26.

The square root of 1221020099 is about 34943.0980166327. The cubic root of 1221020099 is about 1068.8274630583.

The spelling of 1221020099 in words is "one billion, two hundred twenty-one million, twenty thousand, ninety-nine".