6690355721 has 4 divisors (see below), whose sum is σ = 7646120832. Its totient is φ = 5734590612.

The previous prime is 6690355673. The next prime is 6690355733. The reversal of 6690355721 is 1275530966.

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 6690355721 - 2⁶ = 6690355657 is a prime.

It is not an unprimeable number, because it can be changed into a prime (6690355741) 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, 477882545 + ... + 477882558.

It is an arithmetic number, because the mean of its divisors is an integer number (1911530208).

Almost surely, 2^6690355721 is an apocalyptic number.

It is an amenable number.

6690355721 is a deficient number, since it is larger than the sum of its proper divisors (955765111).

6690355721 is an equidigital number, since it uses as much as digits as its factorization.

6690355721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 955765110.

The product of its (nonzero) digits is 340200, while the sum is 44.

The square root of 6690355721 is about 81794.5946930480. The cubic root of 6690355721 is about 1884.2986479119.

The spelling of 6690355721 in words is "six billion, six hundred ninety million, three hundred fifty-five thousand, seven hundred twenty-one".