6651637221 has 16 divisors (see below), whose sum is σ = 8930001024. Its totient is φ = 4403897664.

The previous prime is 6651637199. The next prime is 6651637231. The reversal of 6651637221 is 1227361566.

It is not a de Polignac number, because 6651637221 - 2⁹ = 6651636709 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 6651637221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6651637231) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 614371 + ... + 625103.

It is an arithmetic number, because the mean of its divisors is an integer number (558125064).

Almost surely, 2^6651637221 is an apocalyptic number.

It is an amenable number.

6651637221 is a deficient number, since it is larger than the sum of its proper divisors (2278363803).

6651637221 is a wasteful number, since it uses less digits than its factorization.

6651637221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12140.

The product of its digits is 90720, while the sum is 39.

The square root of 6651637221 is about 81557.5699797389. The cubic root of 6651637221 is about 1880.6566686162.

Adding to 6651637221 its reverse (1227361566), we get a palindrome (7878998787).

The spelling of 6651637221 in words is "six billion, six hundred fifty-one million, six hundred thirty-seven thousand, two hundred twenty-one".