21544947 has 10 divisors (see below), whose sum is σ = 32184548. Its totient is φ = 14363244.

The previous prime is 21544937. The next prime is 21544949. The reversal of 21544947 is 74944512.

It is a happy number.

21544947 is a `hidden beast` number, since 21 + 544 + 94 + 7 = 666.

It is not a de Polignac number, because 21544947 - 2⁴ = 21544931 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21544949) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 132913 + ... + 133074.

Almost surely, 2^21544947 is an apocalyptic number.

21544947 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

21544947 is a deficient number, since it is larger than the sum of its proper divisors (10639601).

21544947 is an equidigital number, since it uses as much as digits as its factorization.

21544947 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 265999 (or 265990 counting only the distinct ones).

The product of its digits is 40320, while the sum is 36.

The square root of 21544947 is about 4641.6534769412. The cubic root of 21544947 is about 278.2585237252.

It can be divided in two parts, 215449 and 47, that added together give a triangular number (215496 = T₆₅₆).

The spelling of 21544947 in words is "twenty-one million, five hundred forty-four thousand, nine hundred forty-seven".