21018552 has 16 divisors (see below), whose sum is σ = 52546440. Its totient is φ = 7006176.

The previous prime is 21018551. The next prime is 21018563. The reversal of 21018552 is 25581012.

It is a Harshad number since it is a multiple of its sum of digits (24), and also a Moran number because the ratio is a prime number: 875773 = 21018552 / (2 + 1 + 0 + 1 + 8 + 5 + 5 + 2).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21018551) 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, 437863 + ... + 437910.

Almost surely, 2^21018552 is an apocalyptic number.

It is an amenable number.

21018552 is an abundant number, since it is smaller than the sum of its proper divisors (31527888).

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

21018552 is a wasteful number, since it uses less digits than its factorization.

21018552 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 875782 (or 875778 counting only the distinct ones).

The product of its (nonzero) digits is 800, while the sum is 24.

The square root of 21018552 is about 4584.5994372464. The cubic root of 21018552 is about 275.9736374736.

Adding to 21018552 its reverse (25581012), we get a palindrome (46599564).

The spelling of 21018552 in words is "twenty-one million, eighteen thousand, five hundred fifty-two".