21156655 has 8 divisors (see below), whose sum is σ = 27340992. Its totient is φ = 15623328.

The previous prime is 21156647. The next prime is 21156661. The reversal of 21156655 is 55665112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21156655 - 2³ = 21156647 is a prime.

It is a Duffinian number.

It is a congruent number.

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 7 ways as a sum of consecutive naturals, for example, 162679 + ... + 162808.

It is an arithmetic number, because the mean of its divisors is an integer number (3417624).

Almost surely, 2^21156655 is an apocalyptic number.

21156655 is a deficient number, since it is larger than the sum of its proper divisors (6184337).

21156655 is a wasteful number, since it uses less digits than its factorization.

21156655 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 325505.

The product of its digits is 9000, while the sum is 31.

The square root of 21156655 is about 4599.6363986733. The cubic root of 21156655 is about 276.5767493802.

The spelling of 21156655 in words is "twenty-one million, one hundred fifty-six thousand, six hundred fifty-five".