21061618 has 16 divisors (see below), whose sum is σ = 32663736. Its totient is φ = 10178560.

The previous prime is 21061613. The next prime is 21061619. The reversal of 21061618 is 81616012.

It can be written as a sum of positive squares in 4 ways, for example, as 10712529 + 10349089 = 3273^2 + 3217^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21061592 and 21061601.

It is not an unprimeable number, because it can be changed into a prime (21061613) 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, 8130 + ... + 10402.

Almost surely, 2^21061618 is an apocalyptic number.

21061618 is a deficient number, since it is larger than the sum of its proper divisors (11602118).

21061618 is a wasteful number, since it uses less digits than its factorization.

21061618 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2429.

The product of its (nonzero) digits is 576, while the sum is 25.

The square root of 21061618 is about 4589.2938454625. The cubic root of 21061618 is about 276.1619944480.

The spelling of 21061618 in words is "twenty-one million, sixty-one thousand, six hundred eighteen".