21258155 has 4 divisors (see below), whose sum is σ = 25509792. Its totient is φ = 17006520.

The previous prime is 21258151. The next prime is 21258173. The reversal of 21258155 is 55185212.

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

It is not a de Polignac number, because 21258155 - 2² = 21258151 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21258151) 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, 2125811 + ... + 2125820.

It is an arithmetic number, because the mean of its divisors is an integer number (6377448).

Almost surely, 2^21258155 is an apocalyptic number.

21258155 is a deficient number, since it is larger than the sum of its proper divisors (4251637).

21258155 is an equidigital number, since it uses as much as digits as its factorization.

21258155 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4251636.

The product of its digits is 4000, while the sum is 29.

The square root of 21258155 is about 4610.6566777413. The cubic root of 21258155 is about 277.0183403949.

The spelling of 21258155 in words is "twenty-one million, two hundred fifty-eight thousand, one hundred fifty-five".