6401621 has 2 divisors, whose sum is σ = 6401622. Its totient is φ = 6401620.

The previous prime is 6401609. The next prime is 6401669. The reversal of 6401621 is 1261046.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 5340721 + 1060900 = 2311^2 + 1030^2 .

It is a cyclic number.

It is not a de Polignac number, because 6401621 - 2⁶ = 6401557 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 6401593 and 6401602.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6401921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3200810 + 3200811.

It is an arithmetic number, because the mean of its divisors is an integer number (3200811).

Almost surely, 2^6401621 is an apocalyptic number.

It is an amenable number.

6401621 is a deficient number, since it is larger than the sum of its proper divisors (1).

6401621 is an equidigital number, since it uses as much as digits as its factorization.

6401621 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 288, while the sum is 20.

The square root of 6401621 is about 2530.1424861063. The cubic root of 6401621 is about 185.6792270536.

Adding to 6401621 its reverse (1261046), we get a palindrome (7662667).

The spelling of 6401621 in words is "six million, four hundred one thousand, six hundred twenty-one".