21534839 has 2 divisors, whose sum is σ = 21534840. Its totient is φ = 21534838.

The previous prime is 21534833. The next prime is 21534841. The reversal of 21534839 is 93843512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21534839 - 2¹⁶ = 21469303 is a prime.

It is a Sophie Germain prime.

Together with 21534841, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21534799 and 21534808.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21534833) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10767419 + 10767420.

It is an arithmetic number, because the mean of its divisors is an integer number (10767420).

Almost surely, 2^21534839 is an apocalyptic number.

21534839 is a deficient number, since it is larger than the sum of its proper divisors (1).

21534839 is an equidigital number, since it uses as much as digits as its factorization.

21534839 is an evil number, because the sum of its binary digits is even.

The product of its digits is 25920, while the sum is 35.

The square root of 21534839 is about 4640.5645130738. The cubic root of 21534839 is about 278.2150011128.

It can be divided in two parts, 215 and 34839, that multiplied together give a triangular number (7490385 = T₃₈₇₀).

The spelling of 21534839 in words is "twenty-one million, five hundred thirty-four thousand, eight hundred thirty-nine".