21490123 has 4 divisors (see below), whose sum is σ = 21503440. Its totient is φ = 21476808.

The previous prime is 21490103. The next prime is 21490129. The reversal of 21490123 is 32109412.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21490123 is a prime.

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

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21490094 and 21490103.

It is not an unprimeable number, because it can be changed into a prime (21490129) 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, 3840 + ... + 7597.

It is an arithmetic number, because the mean of its divisors is an integer number (5375860).

Almost surely, 2^21490123 is an apocalyptic number.

21490123 is a deficient number, since it is larger than the sum of its proper divisors (13317).

21490123 is a wasteful number, since it uses less digits than its factorization.

21490123 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13316.

The product of its (nonzero) digits is 432, while the sum is 22.

The square root of 21490123 is about 4635.7440610974. The cubic root of 21490123 is about 278.0223012318.

Adding to 21490123 its reverse (32109412), we get a palindrome (53599535).

The spelling of 21490123 in words is "twenty-one million, four hundred ninety thousand, one hundred twenty-three".