6690021 has 8 divisors (see below), whose sum is σ = 9606240. Its totient is φ = 4116912.

The previous prime is 6690001. The next prime is 6690029. The reversal of 6690021 is 1200966.

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

It is not a de Polignac number, because 6690021 - 2⁵ = 6689989 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 6689973 and 6690000.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6690029) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 85731 + ... + 85808.

It is an arithmetic number, because the mean of its divisors is an integer number (1200780).

Almost surely, 2^6690021 is an apocalyptic number.

It is an amenable number.

6690021 is a deficient number, since it is larger than the sum of its proper divisors (2916219).

6690021 is a wasteful number, since it uses less digits than its factorization.

6690021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 171555.

The product of its (nonzero) digits is 648, while the sum is 24.

The square root of 6690021 is about 2586.5074908069. The cubic root of 6690021 is about 188.4267223332.

Adding to 6690021 its reverse (1200966), we get a palindrome (7890987).

The spelling of 6690021 in words is "six million, six hundred ninety thousand, twenty-one".