1221742638 has 24 divisors (see below), whose sum is σ = 2802822048. Its totient is φ = 383291712.

The previous prime is 1221742619. The next prime is 1221742651. The reversal of 1221742638 is 8362471221.

It is a happy number.

1221742638 is a `hidden beast` number, since 1 + 2 + 2 + 17 + 4 + 2 + 638 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1996006 + ... + 1996617.

It is an arithmetic number, because the mean of its divisors is an integer number (116784252).

Almost surely, 2^1221742638 is an apocalyptic number.

1221742638 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

1221742638 is an abundant number, since it is smaller than the sum of its proper divisors (1581079410).

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

1221742638 is a wasteful number, since it uses less digits than its factorization.

1221742638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3992648 (or 3992645 counting only the distinct ones).

The product of its digits is 32256, while the sum is 36.

The square root of 1221742638 is about 34953.4352818146. The cubic root of 1221742638 is about 1069.0382478076.

The spelling of 1221742638 in words is "one billion, two hundred twenty-one million, seven hundred forty-two thousand, six hundred thirty-eight".