1221543664 has 20 divisors (see below), whose sum is σ = 2581899480. Its totient is φ = 555247040.

The previous prime is 1221543637. The next prime is 1221543667. The reversal of 1221543664 is 4663451221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221543667) 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, 3470119 + ... + 3470470.

It is an arithmetic number, because the mean of its divisors is an integer number (129094974).

Almost surely, 2^1221543664 is an apocalyptic number.

It is an amenable number.

1221543664 is an abundant number, since it is smaller than the sum of its proper divisors (1360355816).

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

1221543664 is a wasteful number, since it uses less digits than its factorization.

1221543664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6940608 (or 6940602 counting only the distinct ones).

The product of its digits is 34560, while the sum is 34.

The square root of 1221543664 is about 34950.5888934650. The cubic root of 1221543664 is about 1068.9802098438.

Adding to 1221543664 its reverse (4663451221), we get a palindrome (5884994885).

The spelling of 1221543664 in words is "one billion, two hundred twenty-one million, five hundred forty-three thousand, six hundred sixty-four".