21540847 has 2 divisors, whose sum is σ = 21540848. Its totient is φ = 21540846.

The previous prime is 21540833. The next prime is 21540859. The reversal of 21540847 is 74804512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21540847 - 2²³ = 13152239 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21540817) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10770423 + 10770424.

It is an arithmetic number, because the mean of its divisors is an integer number (10770424).

Almost surely, 2^21540847 is an apocalyptic number.

21540847 is a deficient number, since it is larger than the sum of its proper divisors (1).

21540847 is an equidigital number, since it uses as much as digits as its factorization.

21540847 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8960, while the sum is 31.

The square root of 21540847 is about 4641.2118029670. The cubic root of 21540847 is about 278.2408717544.

The spelling of 21540847 in words is "twenty-one million, five hundred forty thousand, eight hundred forty-seven".