1221621640 has 16 divisors (see below), whose sum is σ = 2748648780. Its totient is φ = 488648640.

The previous prime is 1221621631. The next prime is 1221621641. The reversal of 1221621640 is 461261221.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 1142304804 + 79316836 = 33798^2 + 8906^2 .

It is not an unprimeable number, because it can be changed into a prime (1221621641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15270231 + ... + 15270310.

Almost surely, 2^1221621640 is an apocalyptic number.

1221621640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1221621640 is an abundant number, since it is smaller than the sum of its proper divisors (1527027140).

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

1221621640 is a wasteful number, since it uses less digits than its factorization.

1221621640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30540552 (or 30540548 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 25.

The square root of 1221621640 is about 34951.7043933483. The cubic root of 1221621640 is about 1069.0029551154.

Adding to 1221621640 its reverse (461261221), we get a palindrome (1682882861).

It can be divided in two parts, 12216 and 21640, that added together give a square (33856 = 184²).

The spelling of 1221621640 in words is "one billion, two hundred twenty-one million, six hundred twenty-one thousand, six hundred forty".