21299551 has 32 divisors (see below), whose sum is σ = 28098560. Its totient is φ = 15676416.

The previous prime is 21299549. The next prime is 21299557. The reversal of 21299551 is 15599212.

It is not a de Polignac number, because 21299551 - 2¹ = 21299549 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21299557) by changing a digit.

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 in 31 ways as a sum of consecutive naturals, for example, 167650 + ... + 167776.

It is an arithmetic number, because the mean of its divisors is an integer number (878080).

Almost surely, 2^21299551 is an apocalyptic number.

21299551 is a deficient number, since it is larger than the sum of its proper divisors (6799009).

21299551 is a wasteful number, since it uses less digits than its factorization.

21299551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 263.

The product of its digits is 8100, while the sum is 34.

The square root of 21299551 is about 4615.1436597358. The cubic root of 21299551 is about 277.1980363867.

The spelling of 21299551 in words is "twenty-one million, two hundred ninety-nine thousand, five hundred fifty-one".