1221663644 has 12 divisors (see below), whose sum is σ = 2141753544. Its totient is φ = 609734064.

The previous prime is 1221663623. The next prime is 1221663649. The reversal of 1221663644 is 4463661221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221663649) 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, 271934 + ... + 276389.

It is an arithmetic number, because the mean of its divisors is an integer number (178479462).

Almost surely, 2^1221663644 is an apocalyptic number.

It is an amenable number.

1221663644 is a deficient number, since it is larger than the sum of its proper divisors (920089900).

1221663644 is a wasteful number, since it uses less digits than its factorization.

1221663644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 548884 (or 548882 counting only the distinct ones).

The product of its digits is 41472, while the sum is 35.

The square root of 1221663644 is about 34952.3052744737. The cubic root of 1221663644 is about 1069.0152071047.

The spelling of 1221663644 in words is "one billion, two hundred twenty-one million, six hundred sixty-three thousand, six hundred forty-four".