21618719 has 4 divisors (see below), whose sum is σ = 21923280. Its totient is φ = 21314160.

The previous prime is 21618703. The next prime is 21618739. The reversal of 21618719 is 91781612.

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

It is a cyclic number.

It is not a de Polignac number, because 21618719 - 2⁴ = 21618703 is a prime.

It is a super-2 number, since 2×21618719² = 934738022401922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21618739) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 152174 + ... + 152315.

It is an arithmetic number, because the mean of its divisors is an integer number (5480820).

Almost surely, 2^21618719 is an apocalyptic number.

21618719 is a deficient number, since it is larger than the sum of its proper divisors (304561).

21618719 is an equidigital number, since it uses as much as digits as its factorization.

21618719 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 304560.

The product of its digits is 6048, while the sum is 35.

The square root of 21618719 is about 4649.5934230855. The cubic root of 21618719 is about 278.5757566968.

The spelling of 21618719 in words is "twenty-one million, six hundred eighteen thousand, seven hundred nineteen".