21847957 has 8 divisors (see below), whose sum is σ = 22464792. Its totient is φ = 21247840.

The previous prime is 21847939. The next prime is 21847961. The reversal of 21847957 is 75974812.

It can be written as a sum of positive squares in 4 ways, for example, as 17690436 + 4157521 = 4206^2 + 2039^2 .

It is not a de Polignac number, because 21847957 - 2¹¹ = 21845909 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21847927) 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, 68763 + ... + 69079.

It is an arithmetic number, because the mean of its divisors is an integer number (2808099).

Almost surely, 2^21847957 is an apocalyptic number.

It is an amenable number.

21847957 is a deficient number, since it is larger than the sum of its proper divisors (616835).

21847957 is an frugal number, since it uses more digits than its factorization.

21847957 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 440 (or 358 counting only the distinct ones).

The product of its digits is 141120, while the sum is 43.

The square root of 21847957 is about 4674.1798211023. The cubic root of 21847957 is about 279.5569395955.

The spelling of 21847957 in words is "twenty-one million, eight hundred forty-seven thousand, nine hundred fifty-seven".