1221043664 has 40 divisors (see below), whose sum is σ = 2509378080. Its totient is φ = 573955200.

The previous prime is 1221043613. The next prime is 1221043727. The reversal of 1221043664 is 4663401221.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 24494 + ... + 55154.

It is an arithmetic number, because the mean of its divisors is an integer number (62734452).

Almost surely, 2^1221043664 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1221043664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1254689040).

1221043664 is an abundant number, since it is smaller than the sum of its proper divisors (1288334416).

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

1221043664 is a wasteful number, since it uses less digits than its factorization.

1221043664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30819 (or 30813 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 29.

The square root of 1221043664 is about 34943.4352060584. The cubic root of 1221043664 is about 1068.8343389367.

Adding to 1221043664 its reverse (4663401221), we get a palindrome (5884444885).

The spelling of 1221043664 in words is "one billion, two hundred twenty-one million, forty-three thousand, six hundred sixty-four".