1221638423 has 2 divisors, whose sum is σ = 1221638424. Its totient is φ = 1221638422.

The previous prime is 1221638389. The next prime is 1221638437. The reversal of 1221638423 is 3248361221.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1221638423 - 2¹² = 1221634327 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1221638423.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1221638623) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610819211 + 610819212.

It is an arithmetic number, because the mean of its divisors is an integer number (610819212).

Almost surely, 2^1221638423 is an apocalyptic number.

1221638423 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221638423 is an equidigital number, since it uses as much as digits as its factorization.

1221638423 is an evil number, because the sum of its binary digits is even.

The product of its digits is 13824, while the sum is 32.

The square root of 1221638423 is about 34951.9444809584. The cubic root of 1221638423 is about 1069.0078505194.

Adding to 1221638423 its reverse (3248361221), we get a palindrome (4469999644).

The spelling of 1221638423 in words is "one billion, two hundred twenty-one million, six hundred thirty-eight thousand, four hundred twenty-three".