21261830 has 16 divisors (see below), whose sum is σ = 38921040. Its totient is φ = 8360352.

The previous prime is 21261827. The next prime is 21261839. The reversal of 21261830 is 3816212.

It is a junction number, because it is equal to n+sod(n) for n = 21261796 and 21261805.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21261839) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 17429 + ... + 18608.

It is an arithmetic number, because the mean of its divisors is an integer number (2432565).

Almost surely, 2^21261830 is an apocalyptic number.

21261830 is a deficient number, since it is larger than the sum of its proper divisors (17659210).

21261830 is a wasteful number, since it uses less digits than its factorization.

21261830 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36103.

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 21261830 is about 4611.0551937707. The cubic root of 21261830 is about 277.0343026415.

The spelling of 21261830 in words is "twenty-one million, two hundred sixty-one thousand, eight hundred thirty".