21771983 has 2 divisors, whose sum is σ = 21771984. Its totient is φ = 21771982.

The previous prime is 21771977. The next prime is 21772001. The reversal of 21771983 is 38917712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21771983 - 2⁸ = 21771727 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21771913) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10885991 + 10885992.

It is an arithmetic number, because the mean of its divisors is an integer number (10885992).

Almost surely, 2^21771983 is an apocalyptic number.

21771983 is a deficient number, since it is larger than the sum of its proper divisors (1).

21771983 is an equidigital number, since it uses as much as digits as its factorization.

21771983 is an evil number, because the sum of its binary digits is even.

The product of its digits is 21168, while the sum is 38.

The square root of 21771983 is about 4666.0457563123. The cubic root of 21771983 is about 279.2325198572.

The spelling of 21771983 in words is "twenty-one million, seven hundred seventy-one thousand, nine hundred eighty-three".