21452381 has 4 divisors (see below), whose sum is σ = 21504000. Its totient is φ = 21400764.

The previous prime is 21452363. The next prime is 21452393. The reversal of 21452381 is 18325412.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21452381 - 2¹⁰ = 21451357 is a prime.

It is a super-2 number, since 2×21452381² = 920409301138322, which contains 22 as substring.

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

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21452381.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21422381) 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, 25181 + ... + 26018.

It is an arithmetic number, because the mean of its divisors is an integer number (5376000).

Almost surely, 2^21452381 is an apocalyptic number.

It is an amenable number.

21452381 is a deficient number, since it is larger than the sum of its proper divisors (51619).

21452381 is an equidigital number, since it uses as much as digits as its factorization.

21452381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51618.

The product of its digits is 1920, while the sum is 26.

The square root of 21452381 is about 4631.6715125319. The cubic root of 21452381 is about 277.8594470913.

Adding to 21452381 its reverse (18325412), we get a palindrome (39777793).

The spelling of 21452381 in words is "twenty-one million, four hundred fifty-two thousand, three hundred eighty-one".