21870123 has 16 divisors (see below), whose sum is σ = 32217600. Its totient is φ = 13085280.

The previous prime is 21870103. The next prime is 21870127. The reversal of 21870123 is 32107812.

It is not a de Polignac number, because 21870123 - 2⁵ = 21870091 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a junction number, because it is equal to n+sod(n) for n = 21870093 and 21870102.

It is not an unprimeable number, because it can be changed into a prime (21870127) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1588 + ... + 6801.

It is an arithmetic number, because the mean of its divisors is an integer number (2013600).

Almost surely, 2^21870123 is an apocalyptic number.

21870123 is a deficient number, since it is larger than the sum of its proper divisors (10347477).

21870123 is a wasteful number, since it uses less digits than its factorization.

21870123 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8482.

The product of its (nonzero) digits is 672, while the sum is 24.

The square root of 21870123 is about 4676.5503311736. The cubic root of 21870123 is about 279.6514498004.

Adding to 21870123 its reverse (32107812), we get a palindrome (53977935).

The spelling of 21870123 in words is "twenty-one million, eight hundred seventy thousand, one hundred twenty-three".