1243405521 has 6 divisors (see below), whose sum is σ = 1796030210. Its totient is φ = 828937008.

The previous prime is 1243405489. The next prime is 1243405549. The reversal of 1243405521 is 1255043421.

It can be written as a sum of positive squares in only one way, i.e., 690638400 + 552767121 = 26280^2 + 23511^2 .

It is not a de Polignac number, because 1243405521 - 2⁵ = 1243405489 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1243405621) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 69078076 + ... + 69078093.

Almost surely, 2^1243405521 is an apocalyptic number.

It is an amenable number.

1243405521 is a deficient number, since it is larger than the sum of its proper divisors (552624689).

1243405521 is a wasteful number, since it uses less digits than its factorization.

1243405521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 138156175 (or 138156172 counting only the distinct ones).

The product of its (nonzero) digits is 4800, while the sum is 27.

The square root of 1243405521 is about 35261.9557171748. The cubic root of 1243405521 is about 1075.3196874338.

Adding to 1243405521 its reverse (1255043421), we get a palindrome (2498448942).

Subtracting 1243405521 from its reverse (1255043421), we obtain a triangular number (11637900 = T₄₈₂₄).

The spelling of 1243405521 in words is "one billion, two hundred forty-three million, four hundred five thousand, five hundred twenty-one".