21150810 has 24 divisors (see below), whose sum is σ = 54992340. Its totient is φ = 5640192.

The previous prime is 21150809. The next prime is 21150817. The reversal of 21150810 is 1805112.

It can be written as a sum of positive squares in 2 ways, for example, as 21150801 + 9 = 4599^2 + 3^2 .

It is a super-2 number, since 2×21150810² = 894713527312200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21150817) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 117415 + ... + 117594.

Almost surely, 2^21150810 is an apocalyptic number.

21150810 is an abundant number, since it is smaller than the sum of its proper divisors (33841530).

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

21150810 is a wasteful number, since it uses less digits than its factorization.

21150810 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 235022 (or 235019 counting only the distinct ones).

The product of its (nonzero) digits is 80, while the sum is 18.

The square root of 21150810 is about 4599.0009784735. Note that the first 3 decimals coincide. The cubic root of 21150810 is about 276.5512768595.

Adding to 21150810 its reverse (1805112), we get a palindrome (22955922).

The spelling of 21150810 in words is "twenty-one million, one hundred fifty thousand, eight hundred ten".