21618129 has 16 divisors (see below), whose sum is σ = 32044544. Its totient is φ = 12873600.

The previous prime is 21618127. The next prime is 21618133. The reversal of 21618129 is 92181612.

It is a happy number.

It is not a de Polignac number, because 21618129 - 2¹ = 21618127 is a prime.

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

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21618096 and 21618105.

It is not an unprimeable number, because it can be changed into a prime (21618127) 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, 7732 + ... + 10149.

It is an arithmetic number, because the mean of its divisors is an integer number (2002784).

Almost surely, 2^21618129 is an apocalyptic number.

It is an amenable number.

21618129 is a deficient number, since it is larger than the sum of its proper divisors (10426415).

21618129 is a wasteful number, since it uses less digits than its factorization.

21618129 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17928.

The product of its digits is 1728, while the sum is 30.

The square root of 21618129 is about 4649.5299762449. The cubic root of 21618129 is about 278.5732224549.

The spelling of 21618129 in words is "twenty-one million, six hundred eighteen thousand, one hundred twenty-nine".