21123481 has 4 divisors (see below), whose sum is σ = 21169764. Its totient is φ = 21077200.

The previous prime is 21123467. The next prime is 21123491. The reversal of 21123481 is 18432112.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 16128256 + 4995225 = 4016^2 + 2235^2 .

It is a cyclic number.

It is not a de Polignac number, because 21123481 - 2²³ = 12734873 is a prime.

It is a super-2 number, since 2×21123481² = 892402899114722, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21123461) 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, 22450 + ... + 23371.

It is an arithmetic number, because the mean of its divisors is an integer number (5292441).

Almost surely, 2^21123481 is an apocalyptic number.

It is an amenable number.

21123481 is a deficient number, since it is larger than the sum of its proper divisors (46283).

21123481 is an equidigital number, since it uses as much as digits as its factorization.

21123481 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 46282.

The product of its digits is 384, while the sum is 22.

The square root of 21123481 is about 4596.0288293265. The cubic root of 21123481 is about 276.4321147193.

Adding to 21123481 its reverse (18432112), we get a palindrome (39555593).

The spelling of 21123481 in words is "twenty-one million, one hundred twenty-three thousand, four hundred eighty-one".