21538947 has 8 divisors (see below), whose sum is σ = 29015056. Its totient is φ = 14211072.

The previous prime is 21538943. The next prime is 21538961. The reversal of 21538947 is 74983512.

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

It is not a de Polignac number, because 21538947 - 2² = 21538943 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21538943) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 36718 + ... + 37299.

It is an arithmetic number, because the mean of its divisors is an integer number (3626882).

Almost surely, 2^21538947 is an apocalyptic number.

21538947 is a deficient number, since it is larger than the sum of its proper divisors (7476109).

21538947 is an equidigital number, since it uses as much as digits as its factorization.

21538947 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 74117.

The product of its digits is 60480, while the sum is 39.

The square root of 21538947 is about 4641.0071105311. The cubic root of 21538947 is about 278.2326908134.

The spelling of 21538947 in words is "twenty-one million, five hundred thirty-eight thousand, nine hundred forty-seven".