21040655 has 4 divisors (see below), whose sum is σ = 25248792. Its totient is φ = 16832520.

The previous prime is 21040651. The next prime is 21040673. The reversal of 21040655 is 55604012.

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

It is not a de Polignac number, because 21040655 - 2² = 21040651 is a prime.

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 21040655.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21040651) 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, 2104061 + ... + 2104070.

It is an arithmetic number, because the mean of its divisors is an integer number (6312198).

Almost surely, 2^21040655 is an apocalyptic number.

21040655 is a deficient number, since it is larger than the sum of its proper divisors (4208137).

21040655 is an equidigital number, since it uses as much as digits as its factorization.

21040655 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4208136.

The product of its (nonzero) digits is 1200, while the sum is 23.

The square root of 21040655 is about 4587.0093743091. The cubic root of 21040655 is about 276.0703410646.

Adding to 21040655 its reverse (55604012), we get a palindrome (76644667).

The spelling of 21040655 in words is "twenty-one million, forty thousand, six hundred fifty-five".