21156554 has 4 divisors (see below), whose sum is σ = 31734834. Its totient is φ = 10578276.

The previous prime is 21156529. The next prime is 21156589. The reversal of 21156554 is 45565112.

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 only one way, i.e., 20043529 + 1113025 = 4477^2 + 1055^2 .

It is an unprimeable number.

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 as a sum of consecutive naturals, namely, 5289137 + ... + 5289140.

Almost surely, 2^21156554 is an apocalyptic number.

21156554 is a deficient number, since it is larger than the sum of its proper divisors (10578280).

21156554 is a wasteful number, since it uses less digits than its factorization.

21156554 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10578279.

The product of its digits is 6000, while the sum is 29.

The square root of 21156554 is about 4599.6254195315. The cubic root of 21156554 is about 276.5763092618.

It can be divided in two parts, 211 and 56554, that added together give a palindrome (56765).

The spelling of 21156554 in words is "twenty-one million, one hundred fifty-six thousand, five hundred fifty-four".