1221543605 has 16 divisors (see below), whose sum is σ = 1491654528. Its totient is φ = 960072000.

The previous prime is 1221543599. The next prime is 1221543607. The reversal of 1221543605 is 5063451221.

It is not a de Polignac number, because 1221543605 - 2⁶ = 1221543541 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221543607) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 330920 + ... + 334590.

It is an arithmetic number, because the mean of its divisors is an integer number (93228408).

Almost surely, 2^1221543605 is an apocalyptic number.

It is an amenable number.

1221543605 is a deficient number, since it is larger than the sum of its proper divisors (270110923).

1221543605 is a wasteful number, since it uses less digits than its factorization.

1221543605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4828.

The product of its (nonzero) digits is 7200, while the sum is 29.

The square root of 1221543605 is about 34950.5880494163. The cubic root of 1221543605 is about 1068.9801926334.

Adding to 1221543605 its reverse (5063451221), we get a palindrome (6284994826).

The spelling of 1221543605 in words is "one billion, two hundred twenty-one million, five hundred forty-three thousand, six hundred five".