21700643 has 2 divisors, whose sum is σ = 21700644. Its totient is φ = 21700642.

The previous prime is 21700639. The next prime is 21700649. The reversal of 21700643 is 34600712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21700643 - 2² = 21700639 is a prime.

It is a super-2 number, since 2×21700643² = 941835813226898, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21700649) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10850321 + 10850322.

It is an arithmetic number, because the mean of its divisors is an integer number (10850322).

Almost surely, 2^21700643 is an apocalyptic number.

21700643 is a deficient number, since it is larger than the sum of its proper divisors (1).

21700643 is an equidigital number, since it uses as much as digits as its factorization.

21700643 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1008, while the sum is 23.

The square root of 21700643 is about 4658.3948952402. The cubic root of 21700643 is about 278.9272001663.

The spelling of 21700643 in words is "twenty-one million, seven hundred thousand, six hundred forty-three".