7891240021 has 4 divisors (see below), whose sum is σ = 9018560032. Its totient is φ = 6763920012.

The previous prime is 7891240003. The next prime is 7891240031. The reversal of 7891240021 is 1200421987.

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 not a de Polignac number, because 7891240021 - 2²¹ = 7889142869 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 (7891240001) 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, 563659995 + ... + 563660008.

It is an arithmetic number, because the mean of its divisors is an integer number (2254640008).

Almost surely, 2^7891240021 is an apocalyptic number.

It is an amenable number.

7891240021 is a deficient number, since it is larger than the sum of its proper divisors (1127320011).

7891240021 is a wasteful number, since it uses less digits than its factorization.

7891240021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1127320010.

The product of its (nonzero) digits is 8064, while the sum is 34.

The square root of 7891240021 is about 88832.6517728701. The cubic root of 7891240021 is about 1990.8952833796.

The spelling of 7891240021 in words is "seven billion, eight hundred ninety-one million, two hundred forty thousand, twenty-one".