21211755 has 16 divisors (see below), whose sum is σ = 34055424. Its totient is φ = 11274080.

The previous prime is 21211721. The next prime is 21211769. The reversal of 21211755 is 55711212.

It is not a de Polignac number, because 21211755 - 2¹⁴ = 21195371 is a prime.

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 in 15 ways as a sum of consecutive naturals, for example, 2392 + ... + 6938.

It is an arithmetic number, because the mean of its divisors is an integer number (2128464).

Almost surely, 2^21211755 is an apocalyptic number.

21211755 is a deficient number, since it is larger than the sum of its proper divisors (12843669).

21211755 is a wasteful number, since it uses less digits than its factorization.

21211755 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4866.

The product of its digits is 700, while the sum is 24.

The square root of 21211755 is about 4605.6221078156. The cubic root of 21211755 is about 276.8166450266.

Adding to 21211755 its reverse (55711212), we get a palindrome (76922967).

The spelling of 21211755 in words is "twenty-one million, two hundred eleven thousand, seven hundred fifty-five".