1221006640 has 80 divisors (see below), whose sum is σ = 3435262272. Its totient is φ = 394002432.

The previous prime is 1221006637. The next prime is 1221006649. The reversal of 1221006640 is 466001221.

It is a tau number, because it is divible by the number of its divisors (80).

It is not an unprimeable number, because it can be changed into a prime (1221006649) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 54609 + ... + 73648.

Almost surely, 2^1221006640 is an apocalyptic number.

1221006640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1221006640 is an abundant number, since it is smaller than the sum of its proper divisors (2214255632).

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

1221006640 is a wasteful number, since it uses less digits than its factorization.

1221006640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128294 (or 128288 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 22.

The square root of 1221006640 is about 34942.9054315751. The cubic root of 1221006640 is about 1068.8235359044.

Adding to 1221006640 its reverse (466001221), we get a palindrome (1687007861).

The spelling of 1221006640 in words is "one billion, two hundred twenty-one million, six thousand, six hundred forty".