21752381 has 4 divisors (see below), whose sum is σ = 24859872. Its totient is φ = 18644892.

The previous prime is 21752371. The next prime is 21752383. The reversal of 21752381 is 18325712.

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 not a de Polignac number, because 21752381 - 2⁶ = 21752317 is a prime.

It is a super-2 number, since 2×21752381² = 946332158338322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21752383) 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, 1553735 + ... + 1553748.

It is an arithmetic number, because the mean of its divisors is an integer number (6214968).

Almost surely, 2^21752381 is an apocalyptic number.

It is an amenable number.

21752381 is a deficient number, since it is larger than the sum of its proper divisors (3107491).

21752381 is an equidigital number, since it uses as much as digits as its factorization.

21752381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3107490.

The product of its digits is 3360, while the sum is 29.

The square root of 21752381 is about 4663.9447895532. The cubic root of 21752381 is about 279.1486940931.

The spelling of 21752381 in words is "twenty-one million, seven hundred fifty-two thousand, three hundred eighty-one".