6520021 has 6 divisors (see below), whose sum is σ = 6881622. Its totient is φ = 6176520.

The previous prime is 6519991. The next prime is 6520057. The reversal of 6520021 is 1200256.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 6195121 + 324900 = 2489^2 + 570^2 .

It is not a de Polignac number, because 6520021 - 2⁷ = 6519893 is a prime.

It is a Duffinian number.

6520021 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 6519977 and 6520004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6520081) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 8670 + ... + 9391.

It is an arithmetic number, because the mean of its divisors is an integer number (1146937).

Almost surely, 2^6520021 is an apocalyptic number.

It is an amenable number.

6520021 is a deficient number, since it is larger than the sum of its proper divisors (361601).

6520021 is a wasteful number, since it uses less digits than its factorization.

6520021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18099 (or 18080 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 6520021 is about 2553.4331790748. The cubic root of 6520021 is about 186.8169732555.

Adding to 6520021 its reverse (1200256), we get a palindrome (7720277).

The spelling of 6520021 in words is "six million, five hundred twenty thousand, twenty-one".