21395555 has 4 divisors (see below), whose sum is σ = 25674672. Its totient is φ = 17116440.

The previous prime is 21395551. The next prime is 21395587. The reversal of 21395555 is 55559312.

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

It is not a de Polignac number, because 21395555 - 2² = 21395551 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21395551) 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, 2139551 + ... + 2139560.

It is an arithmetic number, because the mean of its divisors is an integer number (6418668).

Almost surely, 2^21395555 is an apocalyptic number.

21395555 is a deficient number, since it is larger than the sum of its proper divisors (4279117).

21395555 is an equidigital number, since it uses as much as digits as its factorization.

21395555 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4279116.

The product of its digits is 33750, while the sum is 35.

The square root of 21395555 is about 4625.5329422673. The cubic root of 21395555 is about 277.6138861065.

The spelling of 21395555 in words is "twenty-one million, three hundred ninety-five thousand, five hundred fifty-five".