21115655 has 16 divisors (see below), whose sum is σ = 27869184. Its totient is φ = 15230880.

The previous prime is 21115651. The next prime is 21115657. The reversal of 21115655 is 55651112.

It is not a de Polignac number, because 21115655 - 2² = 21115651 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21115651) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5474 + ... + 8496.

It is an arithmetic number, because the mean of its divisors is an integer number (1741824).

Almost surely, 2^21115655 is an apocalyptic number.

21115655 is a deficient number, since it is larger than the sum of its proper divisors (6753529).

21115655 is a wasteful number, since it uses less digits than its factorization.

21115655 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3166.

The product of its digits is 1500, while the sum is 26.

The square root of 21115655 is about 4595.1773632799. The cubic root of 21115655 is about 276.3979722256.

Adding to 21115655 its reverse (55651112), we get a palindrome (76766767).

The spelling of 21115655 in words is "twenty-one million, one hundred fifteen thousand, six hundred fifty-five".