21772805 has 4 divisors (see below), whose sum is σ = 26127372. Its totient is φ = 17418240.

The previous prime is 21772787. The next prime is 21772811. The reversal of 21772805 is 50827712.

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 9821956 + 11950849 = 3134^2 + 3457^2 .

It is not a de Polignac number, because 21772805 - 2⁶ = 21772741 is a prime.

It is a Duffinian number.

It is a Curzon 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, 2177276 + ... + 2177285.

It is an arithmetic number, because the mean of its divisors is an integer number (6531843).

Almost surely, 2^21772805 is an apocalyptic number.

It is an amenable number.

21772805 is a deficient number, since it is larger than the sum of its proper divisors (4354567).

21772805 is an equidigital number, since it uses as much as digits as its factorization.

21772805 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4354566.

The product of its (nonzero) digits is 7840, while the sum is 32.

The square root of 21772805 is about 4666.1338386291. The cubic root of 21772805 is about 279.2360339491.

The spelling of 21772805 in words is "twenty-one million, seven hundred seventy-two thousand, eight hundred five".