21630155 has 4 divisors (see below), whose sum is σ = 25956192. Its totient is φ = 17304120.

The previous prime is 21630131. The next prime is 21630179. The reversal of 21630155 is 55103612.

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

It is an interprime number because it is at equal distance from previous prime (21630131) and next prime (21630179).

It is not a de Polignac number, because 21630155 - 2²² = 17435851 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21630155.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2163011 + ... + 2163020.

It is an arithmetic number, because the mean of its divisors is an integer number (6489048).

Almost surely, 2^21630155 is an apocalyptic number.

21630155 is a deficient number, since it is larger than the sum of its proper divisors (4326037).

21630155 is an equidigital number, since it uses as much as digits as its factorization.

21630155 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4326036.

The product of its (nonzero) digits is 900, while the sum is 23.

The square root of 21630155 is about 4650.8230454405. The cubic root of 21630155 is about 278.6248689310.

Adding to 21630155 its reverse (55103612), we get a palindrome (76733767).

The spelling of 21630155 in words is "twenty-one million, six hundred thirty thousand, one hundred fifty-five".