1213644521 has 4 divisors (see below), whose sum is σ = 1224384852. Its totient is φ = 1202904192.

The previous prime is 1213644479. The next prime is 1213644617. The reversal of 1213644521 is 1254463121.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1254463121 = 29 ⋅43257349.

It can be written as a sum of positive squares in 2 ways, for example, as 140754496 + 1072890025 = 11864^2 + 32755^2 .

It is a cyclic number.

It is not a de Polignac number, because 1213644521 - 2²⁶ = 1146535657 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1213644121) 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, 5369996 + ... + 5370221.

It is an arithmetic number, because the mean of its divisors is an integer number (306096213).

Almost surely, 2^1213644521 is an apocalyptic number.

It is an amenable number.

1213644521 is a deficient number, since it is larger than the sum of its proper divisors (10740331).

1213644521 is a wasteful number, since it uses less digits than its factorization.

1213644521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10740330.

The product of its digits is 5760, while the sum is 29.

The square root of 1213644521 is about 34837.4011803406. The cubic root of 1213644521 is about 1066.6710293550.

The spelling of 1213644521 in words is "one billion, two hundred thirteen million, six hundred forty-four thousand, five hundred twenty-one".