21435643 has 2 divisors, whose sum is σ = 21435644. Its totient is φ = 21435642.

The previous prime is 21435593. The next prime is 21435677. The reversal of 21435643 is 34653412.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21435643 - 2¹³ = 21427451 is a prime.

It is not a weakly prime, because it can be changed into another prime (21435143) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10717821 + 10717822.

It is an arithmetic number, because the mean of its divisors is an integer number (10717822).

Almost surely, 2^21435643 is an apocalyptic number.

21435643 is a deficient number, since it is larger than the sum of its proper divisors (1).

21435643 is an equidigital number, since it uses as much as digits as its factorization.

21435643 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8640, while the sum is 28.

The square root of 21435643 is about 4629.8642528696. The cubic root of 21435643 is about 277.7871626281.

It can be divided in two parts, 21 and 435643, that multiplied together give a triangular number (9148503 = T₄₂₇₇).

The spelling of 21435643 in words is "twenty-one million, four hundred thirty-five thousand, six hundred forty-three".