21715418 has 4 divisors (see below), whose sum is σ = 32573130. Its totient is φ = 10857708.

The previous prime is 21715361. The next prime is 21715433. The reversal of 21715418 is 81451712.

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., 18207289 + 3508129 = 4267^2 + 1873^2 .

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5428853 + ... + 5428856.

Almost surely, 2^21715418 is an apocalyptic number.

21715418 is a deficient number, since it is larger than the sum of its proper divisors (10857712).

21715418 is a wasteful number, since it uses less digits than its factorization.

21715418 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10857711.

The product of its digits is 2240, while the sum is 29.

The square root of 21715418 is about 4659.9804720621. The cubic root of 21715418 is about 278.9904888353.

The spelling of 21715418 in words is "twenty-one million, seven hundred fifteen thousand, four hundred eighteen".