21551554 has 4 divisors (see below), whose sum is σ = 32327334. Its totient is φ = 10775776.

The previous prime is 21551539. The next prime is 21551561. The reversal of 21551554 is 45515512.

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., 11458225 + 10093329 = 3385^2 + 3177^2 .

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, 5387887 + ... + 5387890.

Almost surely, 2^21551554 is an apocalyptic number.

21551554 is a deficient number, since it is larger than the sum of its proper divisors (10775780).

21551554 is a wasteful number, since it uses less digits than its factorization.

21551554 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10775779.

The product of its digits is 5000, while the sum is 28.

The square root of 21551554 is about 4642.3651299742. The cubic root of 21551554 is about 278.2869645188.

The spelling of 21551554 in words is "twenty-one million, five hundred fifty-one thousand, five hundred fifty-four".