21648947 has 2 divisors, whose sum is σ = 21648948. Its totient is φ = 21648946.

The previous prime is 21648941. The next prime is 21648997. The reversal of 21648947 is 74984612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21648947 - 2⁴ = 21648931 is a prime.

It is not a weakly prime, because it can be changed into another prime (21648941) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10824473 + 10824474.

It is an arithmetic number, because the mean of its divisors is an integer number (10824474).

Almost surely, 2^21648947 is an apocalyptic number.

21648947 is a deficient number, since it is larger than the sum of its proper divisors (1).

21648947 is an equidigital number, since it uses as much as digits as its factorization.

21648947 is an evil number, because the sum of its binary digits is even.

The product of its digits is 96768, while the sum is 41.

The square root of 21648947 is about 4652.8428944034. The cubic root of 21648947 is about 278.7055341407.

It can be divided in two parts, 2164 and 8947, that added together give a palindrome (11111).

The spelling of 21648947 in words is "twenty-one million, six hundred forty-eight thousand, nine hundred forty-seven".