21777493 has 4 divisors (see below), whose sum is σ = 23058540. Its totient is φ = 20496448.

The previous prime is 21777491. The next prime is 21777517. The reversal of 21777493 is 39477712.

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 8803089 + 12974404 = 2967^2 + 3602^2 .

It is a cyclic number.

It is not a de Polignac number, because 21777493 - 2¹ = 21777491 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 (21777491) 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, 640498 + ... + 640531.

It is an arithmetic number, because the mean of its divisors is an integer number (5764635).

Almost surely, 2^21777493 is an apocalyptic number.

It is an amenable number.

21777493 is a deficient number, since it is larger than the sum of its proper divisors (1281047).

21777493 is a wasteful number, since it uses less digits than its factorization.

21777493 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1281046.

The product of its digits is 74088, while the sum is 40.

The square root of 21777493 is about 4666.6361546622. The cubic root of 21777493 is about 279.2560736972.

The spelling of 21777493 in words is "twenty-one million, seven hundred seventy-seven thousand, four hundred ninety-three".