8421640 has 32 divisors (see below), whose sum is σ = 19073880. Its totient is φ = 3346432.

The previous prime is 8421619. The next prime is 8421641. The reversal of 8421640 is 461248.

It can be written as a sum of positive squares in 4 ways, for example, as 7650756 + 770884 = 2766^2 + 878^2 .

It is not an unprimeable number, because it can be changed into a prime (8421641) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6312 + ... + 7528.

Almost surely, 2^8421640 is an apocalyptic number.

It is an amenable number.

8421640 is an abundant number, since it is smaller than the sum of its proper divisors (10652240).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

8421640 is a wasteful number, since it uses less digits than its factorization.

8421640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1401 (or 1397 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 25.

The square root of 8421640 is about 2902.0062026123. The cubic root of 8421640 is about 203.4536837164.

Adding to 8421640 its reverse (461248), we get a palindrome (8882888).

The spelling of 8421640 in words is "eight million, four hundred twenty-one thousand, six hundred forty".