1221515135 has 4 divisors (see below), whose sum is σ = 1465818168. Its totient is φ = 977212104.

The previous prime is 1221515129. The next prime is 1221515137. The reversal of 1221515135 is 5315151221.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5315151221 = 31 ⋅171456491.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1221515135 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 (1221515137) 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, 122151509 + ... + 122151518.

It is an arithmetic number, because the mean of its divisors is an integer number (366454542).

Almost surely, 2^1221515135 is an apocalyptic number.

1221515135 is a deficient number, since it is larger than the sum of its proper divisors (244303033).

1221515135 is an equidigital number, since it uses as much as digits as its factorization.

1221515135 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 244303032.

The product of its digits is 1500, while the sum is 26.

The square root of 1221515135 is about 34950.1807577586. The cubic root of 1221515135 is about 1068.9718878125.

Adding to 1221515135 its reverse (5315151221), we get a palindrome (6536666356).

The spelling of 1221515135 in words is "one billion, two hundred twenty-one million, five hundred fifteen thousand, one hundred thirty-five".