21455155 has 4 divisors (see below), whose sum is σ = 25746192. Its totient is φ = 17164120.

The previous prime is 21455143. The next prime is 21455183. The reversal of 21455155 is 55155412.

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

It is not a de Polignac number, because 21455155 - 2¹³ = 21446963 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2145511 + ... + 2145520.

It is an arithmetic number, because the mean of its divisors is an integer number (6436548).

Almost surely, 2^21455155 is an apocalyptic number.

21455155 is a deficient number, since it is larger than the sum of its proper divisors (4291037).

21455155 is an equidigital number, since it uses as much as digits as its factorization.

21455155 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4291036.

The product of its digits is 5000, while the sum is 28.

The square root of 21455155 is about 4631.9709627760. The cubic root of 21455155 is about 277.8714232116.

The spelling of 21455155 in words is "twenty-one million, four hundred fifty-five thousand, one hundred fifty-five".