21977843 has 2 divisors, whose sum is σ = 21977844. Its totient is φ = 21977842.

The previous prime is 21977833. The next prime is 21977861. The reversal of 21977843 is 34877912.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21977843 - 2¹⁸ = 21715699 is a prime.

It is a Sophie Germain prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21977843.

It is not a weakly prime, because it can be changed into another prime (21977833) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10988921 + 10988922.

It is an arithmetic number, because the mean of its divisors is an integer number (10988922).

Almost surely, 2^21977843 is an apocalyptic number.

21977843 is a deficient number, since it is larger than the sum of its proper divisors (1).

21977843 is an equidigital number, since it uses as much as digits as its factorization.

21977843 is an evil number, because the sum of its binary digits is even.

The product of its digits is 84672, while the sum is 41.

The square root of 21977843 is about 4688.0532206877. The cubic root of 21977843 is about 280.1098336114.

The spelling of 21977843 in words is "twenty-one million, nine hundred seventy-seven thousand, eight hundred forty-three".