21777245 has 16 divisors (see below), whose sum is σ = 30008448. Its totient is φ = 14861760.

The previous prime is 21777241. The next prime is 21777253. The reversal of 21777245 is 54277712.

It is not a de Polignac number, because 21777245 - 2² = 21777241 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (35).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21777241) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6575 + ... + 9315.

It is an arithmetic number, because the mean of its divisors is an integer number (1875528).

Almost surely, 2^21777245 is an apocalyptic number.

It is an amenable number.

21777245 is a deficient number, since it is larger than the sum of its proper divisors (8231203).

21777245 is a wasteful number, since it uses less digits than its factorization.

21777245 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2980.

The product of its digits is 27440, while the sum is 35.

The square root of 21777245 is about 4666.6095829842. The cubic root of 21777245 is about 279.2550136460.

It can be divided in two parts, 21777 and 245, that added together give a palindrome (22022).

The spelling of 21777245 in words is "twenty-one million, seven hundred seventy-seven thousand, two hundred forty-five".