7821521 has 8 divisors (see below), whose sum is σ = 8308320. Its totient is φ = 7342272.

The previous prime is 7821509. The next prime is 7821523. The reversal of 7821521 is 1251287.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 7821521 - 2¹⁴ = 7805137 is a prime.

It is a super-2 number, since 2×7821521² = 122352381506882, which contains 22 as substring.

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (7821523) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 326 + ... + 3968.

It is an arithmetic number, because the mean of its divisors is an integer number (1038540).

Almost surely, 2^7821521 is an apocalyptic number.

It is an amenable number.

7821521 is a deficient number, since it is larger than the sum of its proper divisors (486799).

7821521 is a wasteful number, since it uses less digits than its factorization.

7821521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3775.

The product of its digits is 1120, while the sum is 26.

The square root of 7821521 is about 2796.6982318441. The cubic root of 7821521 is about 198.5014751586.

The spelling of 7821521 in words is "seven million, eight hundred twenty-one thousand, five hundred twenty-one".