20821643 has 2 divisors, whose sum is σ = 20821644. Its totient is φ = 20821642.

The previous prime is 20821637. The next prime is 20821649. The reversal of 20821643 is 34612802.

It is a balanced prime because it is at equal distance from previous prime (20821637) and next prime (20821649).

It is a cyclic number.

It is not a de Polignac number, because 20821643 - 2⁴ = 20821627 is a prime.

It is not a weakly prime, because it can be changed into another prime (20821649) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10410821 + 10410822.

It is an arithmetic number, because the mean of its divisors is an integer number (10410822).

Almost surely, 2^20821643 is an apocalyptic number.

20821643 is a deficient number, since it is larger than the sum of its proper divisors (1).

20821643 is an equidigital number, since it uses as much as digits as its factorization.

20821643 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2304, while the sum is 26.

The square root of 20821643 is about 4563.0738543223. The cubic root of 20821643 is about 275.1091269379.

The spelling of 20821643 in words is "twenty million, eight hundred twenty-one thousand, six hundred forty-three".