21807938 has 8 divisors (see below), whose sum is σ = 32931900. Its totient is φ = 10830640.

The previous prime is 21807931. The next prime is 21807943. The reversal of 21807938 is 83970812.

It can be written as a sum of positive squares in 2 ways, for example, as 19333609 + 2474329 = 4397^2 + 1573^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a plaindrome in base 11.

It is not an unprimeable number, because it can be changed into a prime (21807931) 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, 36293 + ... + 36888.

Almost surely, 2^21807938 is an apocalyptic number.

21807938 is a deficient number, since it is larger than the sum of its proper divisors (11123962).

21807938 is a wasteful number, since it uses less digits than its factorization.

21807938 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 73332.

The product of its (nonzero) digits is 24192, while the sum is 38.

The square root of 21807938 is about 4669.8970010055. The cubic root of 21807938 is about 279.3861467091.

The spelling of 21807938 in words is "twenty-one million, eight hundred seven thousand, nine hundred thirty-eight".