1213211556 has 36 divisors (see below), whose sum is σ = 3073883904. Its totient is φ = 403460400.

The previous prime is 1213211551. The next prime is 1213211557. The reversal of 1213211556 is 6551123121.

It is a tau number, because it is divible by the number of its divisors (36).

It is a super-2 number, since 2×1213211556² = 2943764559223882272, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (1213211551) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 23580 + ... + 54611.

It is an arithmetic number, because the mean of its divisors is an integer number (85385664).

Almost surely, 2^1213211556 is an apocalyptic number.

It is an amenable number.

1213211556 is an abundant number, since it is smaller than the sum of its proper divisors (1860672348).

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

1213211556 is a wasteful number, since it uses less digits than its factorization.

1213211556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 78632 (or 78627 counting only the distinct ones).

The product of its digits is 1800, while the sum is 27.

The square root of 1213211556 is about 34831.1865430967. The cubic root of 1213211556 is about 1066.5441700910.

Adding to 1213211556 its reverse (6551123121), we get a palindrome (7764334677).

The spelling of 1213211556 in words is "one billion, two hundred thirteen million, two hundred eleven thousand, five hundred fifty-six".