7891021221 has 4 divisors (see below), whose sum is σ = 10521361632. Its totient is φ = 5260680812.

The previous prime is 7891021211. The next prime is 7891021231. The reversal of 7891021221 is 1221201987.

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 an interprime number because it is at equal distance from previous prime (7891021211) and next prime (7891021231).

It is a cyclic number.

It is not a de Polignac number, because 7891021221 - 2¹⁰ = 7891020197 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (7891021211) 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, 1315170201 + ... + 1315170206.

It is an arithmetic number, because the mean of its divisors is an integer number (2630340408).

Almost surely, 2^7891021221 is an apocalyptic number.

It is an amenable number.

7891021221 is a deficient number, since it is larger than the sum of its proper divisors (2630340411).

7891021221 is a wasteful number, since it uses less digits than its factorization.

7891021221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2630340410.

The product of its (nonzero) digits is 4032, while the sum is 33.

The square root of 7891021221 is about 88831.4202351848. The cubic root of 7891021221 is about 1990.8768827263.

The spelling of 7891021221 in words is "seven billion, eight hundred ninety-one million, twenty-one thousand, two hundred twenty-one".