21553769 has 4 divisors (see below), whose sum is σ = 21751620. Its totient is φ = 21355920.

The previous prime is 21553717. The next prime is 21553787. The reversal of 21553769 is 96735512.

It is a happy number.

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 8340544 + 13213225 = 2888^2 + 3635^2 .

It is a cyclic number.

It is not a de Polignac number, because 21553769 - 2²⁰ = 20505193 is a prime.

It is a super-2 number, since 2×21553769² = 929129916210722, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21553789) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 98762 + ... + 98979.

It is an arithmetic number, because the mean of its divisors is an integer number (5437905).

Almost surely, 2^21553769 is an apocalyptic number.

It is an amenable number.

21553769 is a deficient number, since it is larger than the sum of its proper divisors (197851).

21553769 is a wasteful number, since it uses less digits than its factorization.

21553769 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 197850.

The product of its digits is 56700, while the sum is 38.

The square root of 21553769 is about 4642.6036875874. The cubic root of 21553769 is about 278.2964980078.

It can be divided in two parts, 21553 and 769, that added together give a palindrome (22322).

The spelling of 21553769 in words is "twenty-one million, five hundred fifty-three thousand, seven hundred sixty-nine".