21543554 has 4 divisors (see below), whose sum is σ = 32315334. Its totient is φ = 10771776.

The previous prime is 21543551. The next prime is 21543569. The reversal of 21543554 is 45534512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 12075625 + 9467929 = 3475^2 + 3077^2 .

It is not an unprimeable number, because it can be changed into a prime (21543551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5385887 + ... + 5385890.

Almost surely, 2^21543554 is an apocalyptic number.

21543554 is a deficient number, since it is larger than the sum of its proper divisors (10771780).

21543554 is a wasteful number, since it uses less digits than its factorization.

21543554 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10771779.

The product of its digits is 12000, while the sum is 29.

The square root of 21543554 is about 4641.5034202293. The cubic root of 21543554 is about 278.2525266117.

The spelling of 21543554 in words is "twenty-one million, five hundred forty-three thousand, five hundred fifty-four".