21018634 has 32 divisors (see below), whose sum is σ = 39553920. Its totient is φ = 8154432.

The previous prime is 21018631. The next prime is 21018659. The reversal of 21018634 is 43681012.

It is a junction number, because it is equal to n+sod(n) for n = 21018599 and 21018608.

It is not an unprimeable number, because it can be changed into a prime (21018631) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8557 + ... + 10735.

It is an arithmetic number, because the mean of its divisors is an integer number (1236060).

Almost surely, 2^21018634 is an apocalyptic number.

21018634 is a deficient number, since it is larger than the sum of its proper divisors (18535286).

21018634 is a wasteful number, since it uses less digits than its factorization.

21018634 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2254.

The product of its (nonzero) digits is 1152, while the sum is 25.

The square root of 21018634 is about 4584.6083802218. The cubic root of 21018634 is about 275.9739963599.

Adding to 21018634 its reverse (43681012), we get a palindrome (64699646).

The spelling of 21018634 in words is "twenty-one million, eighteen thousand, six hundred thirty-four".