1221786638 has 8 divisors (see below), whose sum is σ = 1841366280. Its totient is φ = 607997880.

The previous prime is 1221786637. The next prime is 1221786647. The reversal of 1221786638 is 8366871221.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221786637) 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, 1447193 + ... + 1448036.

It is an arithmetic number, because the mean of its divisors is an integer number (230170785).

Almost surely, 2^1221786638 is an apocalyptic number.

1221786638 is a deficient number, since it is larger than the sum of its proper divisors (619579642).

1221786638 is a wasteful number, since it uses less digits than its factorization.

1221786638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2895442.

The product of its digits is 193536, while the sum is 44.

The square root of 1221786638 is about 34954.0646849547. The cubic root of 1221786638 is about 1069.0510811482.

The spelling of 1221786638 in words is "one billion, two hundred twenty-one million, seven hundred eighty-six thousand, six hundred thirty-eight".