21147555 has 32 divisors (see below), whose sum is σ = 39755520. Its totient is φ = 9463680.

The previous prime is 21147523. The next prime is 21147559. The reversal of 21147555 is 55574112.

It is not a de Polignac number, because 21147555 - 2⁵ = 21147523 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21147559) by changing a digit.

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 in 31 ways as a sum of consecutive naturals, for example, 2785 + ... + 7074.

It is an arithmetic number, because the mean of its divisors is an integer number (1242360).

Almost surely, 2^21147555 is an apocalyptic number.

21147555 is a deficient number, since it is larger than the sum of its proper divisors (18607965).

21147555 is a wasteful number, since it uses less digits than its factorization.

21147555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9891.

The product of its digits is 7000, while the sum is 30.

The square root of 21147555 is about 4598.6470836541. The cubic root of 21147555 is about 276.5370895291.

It can be divided in two parts, 2114 and 7555, that added together give a palindrome (9669).

The spelling of 21147555 in words is "twenty-one million, one hundred forty-seven thousand, five hundred fifty-five".