21551018 has 4 divisors (see below), whose sum is σ = 32326530. Its totient is φ = 10775508.

The previous prime is 21550939. The next prime is 21551039. The reversal of 21551018 is 81015512.

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., 21132409 + 418609 = 4597^2 + 647^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21550984 and 21551002.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5387753 + ... + 5387756.

Almost surely, 2^21551018 is an apocalyptic number.

21551018 is a deficient number, since it is larger than the sum of its proper divisors (10775512).

21551018 is a wasteful number, since it uses less digits than its factorization.

21551018 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10775511.

The product of its (nonzero) digits is 400, while the sum is 23.

The square root of 21551018 is about 4642.3074004206. The cubic root of 21551018 is about 278.2846574454.

The spelling of 21551018 in words is "twenty-one million, five hundred fifty-one thousand, eighteen".