21810051 has 6 divisors (see below), whose sum is σ = 31503420. Its totient is φ = 14540028.

The previous prime is 21810037. The next prime is 21810053. The reversal of 21810051 is 15001812.

It is not a de Polignac number, because 21810051 - 2⁷ = 21809923 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21810053) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1211661 + ... + 1211678.

It is an arithmetic number, because the mean of its divisors is an integer number (5250570).

Almost surely, 2^21810051 is an apocalyptic number.

21810051 is a deficient number, since it is larger than the sum of its proper divisors (9693369).

21810051 is a wasteful number, since it uses less digits than its factorization.

21810051 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2423345 (or 2423342 counting only the distinct ones).

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

The square root of 21810051 is about 4670.1232317788. The cubic root of 21810051 is about 279.3951697823.

Adding to 21810051 its reverse (15001812), we get a palindrome (36811863).

It can be divided in two parts, 21 and 810051, that multiplied together give a palindrome (17011071).

The spelling of 21810051 in words is "twenty-one million, eight hundred ten thousand, fifty-one".