21764005 has 4 divisors (see below), whose sum is σ = 26116812. Its totient is φ = 17411200.

The previous prime is 21763999. The next prime is 21764021. The reversal of 21764005 is 50046712.

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

It can be written as a sum of positive squares in 2 ways, for example, as 5166529 + 16597476 = 2273^2 + 4074^2 .

It is not a de Polignac number, because 21764005 - 2¹⁹ = 21239717 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2176396 + ... + 2176405.

It is an arithmetic number, because the mean of its divisors is an integer number (6529203).

Almost surely, 2^21764005 is an apocalyptic number.

It is an amenable number.

21764005 is a deficient number, since it is larger than the sum of its proper divisors (4352807).

21764005 is an equidigital number, since it uses as much as digits as its factorization.

21764005 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4352806.

The product of its (nonzero) digits is 1680, while the sum is 25.

The square root of 21764005 is about 4665.1907785213. The cubic root of 21764005 is about 279.1984089052.

It can be divided in two parts, 217 and 64005, that multiplied together give a triangular number (13889085 = T₅₂₇₀).

The spelling of 21764005 in words is "twenty-one million, seven hundred sixty-four thousand, five".