21554 has 8 divisors (see below), whose sum is σ = 34860. Its totient is φ = 9936.

The previous prime is 21529. The next prime is 21557. The reversal of 21554 is 45512.

21554 is an esthetic number in base 16, because in such base its adjacent digits differ by 1.

It can be written as a sum of positive squares in 2 ways, for example, as 21025 + 529 = 145^2 + 23^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a nialpdrome in base 16.

It is not an unprimeable number, because it can be changed into a prime (21557) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 389 + ... + 440.

2²¹⁵⁵⁴ is an apocalyptic number.

21554 is a deficient number, since it is larger than the sum of its proper divisors (13306).

21554 is a wasteful number, since it uses less digits than its factorization.

21554 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 844.

The product of its digits is 200, while the sum is 17.

The square root of 21554 is about 146.8128059809. The cubic root of 21554 is about 27.8297492208.

It can be divided in two parts, 21 and 554, that added together give a palindrome (575).

The spelling of 21554 in words is "twenty-one thousand, five hundred fifty-four".