21455911 has 4 divisors (see below), whose sum is σ = 22195800. Its totient is φ = 20716024.

The previous prime is 21455891. The next prime is 21455927. The reversal of 21455911 is 11955412.

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 21455911 - 2¹³ = 21447719 is a prime.

It is a super-2 number, since 2×21455911² = 920712233679842, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21455911.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21455971) 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, 369901 + ... + 369958.

It is an arithmetic number, because the mean of its divisors is an integer number (5548950).

Almost surely, 2^21455911 is an apocalyptic number.

21455911 is a deficient number, since it is larger than the sum of its proper divisors (739889).

21455911 is an equidigital number, since it uses as much as digits as its factorization.

21455911 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 739888.

The product of its digits is 1800, while the sum is 28.

The square root of 21455911 is about 4632.0525687863. The cubic root of 21455911 is about 277.8746868923.

It can be divided in two parts, 21455 and 911, that added together give a triangular number (22366 = T₂₁₁).

The spelling of 21455911 in words is "twenty-one million, four hundred fifty-five thousand, nine hundred eleven".