21645155 has 16 divisors (see below), whose sum is σ = 30046464. Its totient is φ = 14661600.

The previous prime is 21645133. The next prime is 21645167. The reversal of 21645155 is 55154612.

It is a happy number.

It is not a de Polignac number, because 21645155 - 2⁸ = 21644899 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 821 + ... + 6630.

It is an arithmetic number, because the mean of its divisors is an integer number (1877904).

Almost surely, 2^21645155 is an apocalyptic number.

21645155 is a deficient number, since it is larger than the sum of its proper divisors (8401309).

21645155 is an equidigital number, since it uses as much as digits as its factorization.

21645155 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7546.

The product of its digits is 6000, while the sum is 29.

The square root of 21645155 is about 4652.4353837533. The cubic root of 21645155 is about 278.6892606303.

Adding to 21645155 its reverse (55154612), we get a palindrome (76799767).

The spelling of 21645155 in words is "twenty-one million, six hundred forty-five thousand, one hundred fifty-five".