21063551 has 4 divisors (see below), whose sum is σ = 21109704. Its totient is φ = 21017400.

The previous prime is 21063529. The next prime is 21063569. The reversal of 21063551 is 15536012.

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

It is a cyclic number.

It is not a de Polignac number, because 21063551 - 2¹⁰ = 21062527 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21063521) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 22385 + ... + 23306.

It is an arithmetic number, because the mean of its divisors is an integer number (5277426).

Almost surely, 2^21063551 is an apocalyptic number.

21063551 is a deficient number, since it is larger than the sum of its proper divisors (46153).

21063551 is an equidigital number, since it uses as much as digits as its factorization.

21063551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 46152.

The product of its (nonzero) digits is 900, while the sum is 23.

The square root of 21063551 is about 4589.5044394793. The cubic root of 21063551 is about 276.1704427512.

Adding to 21063551 its reverse (15536012), we get a palindrome (36599563).

The spelling of 21063551 in words is "twenty-one million, sixty-three thousand, five hundred fifty-one".