1221267653 has 4 divisors (see below), whose sum is σ = 1221343788. Its totient is φ = 1221191520.

The previous prime is 1221267643. The next prime is 1221267679. The reversal of 1221267653 is 3567621221.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 3567621221 = 491 ⋅7266031.

It can be written as a sum of positive squares in 2 ways, for example, as 760821889 + 460445764 = 27583^2 + 21458^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221267653 - 2⁴ = 1221267637 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 (1221267643) 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, 3608 + ... + 49553.

It is an arithmetic number, because the mean of its divisors is an integer number (305335947).

Almost surely, 2^1221267653 is an apocalyptic number.

It is an amenable number.

1221267653 is a deficient number, since it is larger than the sum of its proper divisors (76135).

1221267653 is an equidigital number, since it uses as much as digits as its factorization.

1221267653 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 76134.

The product of its digits is 30240, while the sum is 35.

The square root of 1221267653 is about 34946.6400817017. The cubic root of 1221267653 is about 1068.8996908168.

Adding to 1221267653 its reverse (3567621221), we get a palindrome (4788888874).

The spelling of 1221267653 in words is "one billion, two hundred twenty-one million, two hundred sixty-seven thousand, six hundred fifty-three".