6621021 has 24 divisors (see below), whose sum is σ = 10823904. Its totient is φ = 4011120.

The previous prime is 6620981. The next prime is 6621029. The reversal of 6621021 is 1201266.

It is a happy number.

6621021 is a `hidden beast` number, since 662 + 1 + 0 + 2 + 1 = 666.

It is not a de Polignac number, because 6621021 - 2¹⁷ = 6489949 is a prime.

It is an Ulam number.

It is a junction number, because it is equal to n+sod(n) for n = 6620985 and 6621003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6621029) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1435 + ... + 3911.

It is an arithmetic number, because the mean of its divisors is an integer number (450996).

Almost surely, 2^6621021 is an apocalyptic number.

It is an amenable number.

6621021 is a deficient number, since it is larger than the sum of its proper divisors (4202883).

6621021 is a wasteful number, since it uses less digits than its factorization.

6621021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2503 (or 2491 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 18.

The square root of 6621021 is about 2573.1344698636. The cubic root of 6621021 is about 187.7766795242.

Adding to 6621021 its reverse (1201266), we get a palindrome (7822287).

The spelling of 6621021 in words is "six million, six hundred twenty-one thousand, twenty-one".