21071618 has 4 divisors (see below), whose sum is σ = 31607430. Its totient is φ = 10535808.

The previous prime is 21071587. The next prime is 21071621. The reversal of 21071618 is 81617012.

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

It can be written as a sum of positive squares in only one way, i.e., 18292729 + 2778889 = 4277^2 + 1667^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5267903 + ... + 5267906.

Almost surely, 2^21071618 is an apocalyptic number.

21071618 is a deficient number, since it is larger than the sum of its proper divisors (10535812).

21071618 is a wasteful number, since it uses less digits than its factorization.

21071618 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10535811.

The product of its (nonzero) digits is 672, while the sum is 26.

The square root of 21071618 is about 4590.3832084043. The cubic root of 21071618 is about 276.2056945250.

The spelling of 21071618 in words is "twenty-one million, seventy-one thousand, six hundred eighteen".