1243904921 has 4 divisors (see below), whose sum is σ = 1421605632. Its totient is φ = 1066204212.

The previous prime is 1243904891. The next prime is 1243904933. The reversal of 1243904921 is 1294093421.

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.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1243904921 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1243901921) 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, 88850345 + ... + 88850358.

It is an arithmetic number, because the mean of its divisors is an integer number (355401408).

Almost surely, 2^1243904921 is an apocalyptic number.

It is an amenable number.

1243904921 is a deficient number, since it is larger than the sum of its proper divisors (177700711).

1243904921 is an equidigital number, since it uses as much as digits as its factorization.

1243904921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 177700710.

The product of its (nonzero) digits is 15552, while the sum is 35.

The square root of 1243904921 is about 35269.0362924762. The cubic root of 1243904921 is about 1075.4636315624.

The spelling of 1243904921 in words is "one billion, two hundred forty-three million, nine hundred four thousand, nine hundred twenty-one".