21051830 has 8 divisors (see below), whose sum is σ = 37893312. Its totient is φ = 8420728.

The previous prime is 21051809. The next prime is 21051839. The reversal of 21051830 is 3815012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21051839) 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, 1052582 + ... + 1052601.

It is an arithmetic number, because the mean of its divisors is an integer number (4736664).

Almost surely, 2^21051830 is an apocalyptic number.

21051830 is a deficient number, since it is larger than the sum of its proper divisors (16841482).

21051830 is a wasteful number, since it uses less digits than its factorization.

21051830 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2105190.

The product of its (nonzero) digits is 240, while the sum is 20.

The square root of 21051830 is about 4588.2273265391. The cubic root of 21051830 is about 276.1192074148.

Adding to 21051830 its reverse (3815012), we get a palindrome (24866842).

The spelling of 21051830 in words is "twenty-one million, fifty-one thousand, eight hundred thirty".