21764159 has 4 divisors (see below), whose sum is σ = 21791304. Its totient is φ = 21737016.

The previous prime is 21764143. The next prime is 21764179. The reversal of 21764159 is 95146712.

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 21764159 - 2⁴ = 21764143 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21764179) 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, 12332 + ... + 13985.

It is an arithmetic number, because the mean of its divisors is an integer number (5447826).

Almost surely, 2^21764159 is an apocalyptic number.

21764159 is a deficient number, since it is larger than the sum of its proper divisors (27145).

21764159 is an equidigital number, since it uses as much as digits as its factorization.

21764159 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27144.

The product of its digits is 15120, while the sum is 35.

The square root of 21764159 is about 4665.2072837121. The cubic root of 21764159 is about 279.1990674306.

The spelling of 21764159 in words is "twenty-one million, seven hundred sixty-four thousand, one hundred fifty-nine".