21724075 has 12 divisors (see below), whose sum is σ = 28109808. Its totient is φ = 16623200.

The previous prime is 21724057. The next prime is 21724081. The reversal of 21724075 is 57042712.

It is not a de Polignac number, because 21724075 - 2¹⁷ = 21593003 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 18316 + ... + 19465.

It is an arithmetic number, because the mean of its divisors is an integer number (2342484).

Almost surely, 2^21724075 is an apocalyptic number.

21724075 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21724075 is a deficient number, since it is larger than the sum of its proper divisors (6385733).

21724075 is a wasteful number, since it uses less digits than its factorization.

21724075 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37814 (or 37809 counting only the distinct ones).

The product of its (nonzero) digits is 3920, while the sum is 28.

The square root of 21724075 is about 4660.9092460592. The cubic root of 21724075 is about 279.0275577324.

Adding to 21724075 its reverse (57042712), we get a palindrome (78766787).

The spelling of 21724075 in words is "twenty-one million, seven hundred twenty-four thousand, seventy-five".