21043551 has 8 divisors (see below), whose sum is σ = 29278080. Its totient is φ = 13419032.

The previous prime is 21043549. The next prime is 21043559. The reversal of 21043551 is 15534012.

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

It is a cyclic number.

It is not a de Polignac number, because 21043551 - 2¹ = 21043549 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21043559) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 152421 + ... + 152558.

It is an arithmetic number, because the mean of its divisors is an integer number (3659760).

Almost surely, 2^21043551 is an apocalyptic number.

21043551 is a deficient number, since it is larger than the sum of its proper divisors (8234529).

21043551 is a wasteful number, since it uses less digits than its factorization.

21043551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 305005.

The product of its (nonzero) digits is 600, while the sum is 21.

The square root of 21043551 is about 4587.3250375355. The cubic root of 21043551 is about 276.0830064344.

Adding to 21043551 its reverse (15534012), we get a palindrome (36577563).

The spelling of 21043551 in words is "twenty-one million, forty-three thousand, five hundred fifty-one".