8721638 has 4 divisors (see below), whose sum is σ = 13082460. Its totient is φ = 4360818.

The previous prime is 8721631. The next prime is 8721667. The reversal of 8721638 is 8361278.

It is a semiprime because it is the product of two primes.

It is an alternating number because its digits alternate between even and odd.

It is a junction number, because it is equal to n+sod(n) for n = 8721598 and 8721607.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (8721631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2180408 + ... + 2180411.

It is an arithmetic number, because the mean of its divisors is an integer number (3270615).

Almost surely, 2^8721638 is an apocalyptic number.

8721638 is a deficient number, since it is larger than the sum of its proper divisors (4360822).

8721638 is a wasteful number, since it uses less digits than its factorization.

8721638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4360821.

The product of its digits is 16128, while the sum is 35.

The square root of 8721638 is about 2953.2419474198. The cubic root of 8721638 is about 205.8413803924.

The spelling of 8721638 in words is "eight million, seven hundred twenty-one thousand, six hundred thirty-eight".