21030555 has 96 divisors (see below), whose sum is σ = 44126208. Its totient is φ = 8467200.

The previous prime is 21030553. The next prime is 21030557. The reversal of 21030555 is 55503012.

It is an interprime number because it is at equal distance from previous prime (21030553) and next prime (21030557).

It is not a de Polignac number, because 21030555 - 2¹ = 21030553 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is not an unprimeable number, because it can be changed into a prime (21030551) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 296170 + ... + 296240.

It is an arithmetic number, because the mean of its divisors is an integer number (459648).

Almost surely, 2^21030555 is an apocalyptic number.

21030555 is an abundant number, since it is smaller than the sum of its proper divisors (23095653).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21030555 is a wasteful number, since it uses less digits than its factorization.

21030555 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 137 (or 130 counting only the distinct ones).

The product of its (nonzero) digits is 750, while the sum is 21.

The square root of 21030555 is about 4585.9083069769. The cubic root of 21030555 is about 276.0261606163.

Adding to 21030555 its reverse (55503012), we get a palindrome (76533567).

The spelling of 21030555 in words is "twenty-one million, thirty thousand, five hundred fifty-five".