6501721521 has 8 divisors (see below), whose sum is σ = 8669403424. Its totient is φ = 4334260320.

The previous prime is 6501721487. The next prime is 6501721559. The reversal of 6501721521 is 1251271056.

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

It is not a de Polignac number, because 6501721521 - 2⁷ = 6501721393 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (6501721921) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 34290 + ... + 119076.

It is an arithmetic number, because the mean of its divisors is an integer number (1083675428).

Almost surely, 2^6501721521 is an apocalyptic number.

It is an amenable number.

6501721521 is a deficient number, since it is larger than the sum of its proper divisors (2167681903).

6501721521 is a wasteful number, since it uses less digits than its factorization.

6501721521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 110351.

The product of its (nonzero) digits is 4200, while the sum is 30.

The square root of 6501721521 is about 80633.2531961845. The cubic root of 6501721521 is about 1866.4203227458.

Adding to 6501721521 its reverse (1251271056), we get a palindrome (7752992577).

The spelling of 6501721521 in words is "six billion, five hundred one million, seven hundred twenty-one thousand, five hundred twenty-one".