1221455537 has 4 divisors (see below), whose sum is σ = 1221677040. Its totient is φ = 1221234036.

The previous prime is 1221455509. The next prime is 1221455567. The reversal of 1221455537 is 7355541221.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 7355541221 = 7 ⋅1050791603.

It is a cyclic number.

It is not a de Polignac number, because 1221455537 - 2⁸ = 1221455281 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1221455497 and 1221455506.

It is not an unprimeable number, because it can be changed into a prime (1221455567) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 102263 + ... + 113580.

It is an arithmetic number, because the mean of its divisors is an integer number (305419260).

Almost surely, 2^1221455537 is an apocalyptic number.

It is an amenable number.

1221455537 is a deficient number, since it is larger than the sum of its proper divisors (221503).

1221455537 is an equidigital number, since it uses as much as digits as its factorization.

1221455537 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 221502.

The product of its digits is 42000, while the sum is 35.

The square root of 1221455537 is about 34949.3281337424. The cubic root of 1221455537 is about 1068.9545024030.

Adding to 1221455537 its reverse (7355541221), we get a palindrome (8576996758).

The spelling of 1221455537 in words is "one billion, two hundred twenty-one million, four hundred fifty-five thousand, five hundred thirty-seven".