21189977 has 2 divisors, whose sum is σ = 21189978. Its totient is φ = 21189976.

The previous prime is 21189967. The next prime is 21190003. The reversal of 21189977 is 77998112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20894041 + 295936 = 4571^2 + 544^2 .

It is a cyclic number.

It is not a de Polignac number, because 21189977 - 2⁶ = 21189913 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21189947) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10594988 + 10594989.

It is an arithmetic number, because the mean of its divisors is an integer number (10594989).

Almost surely, 2^21189977 is an apocalyptic number.

It is an amenable number.

21189977 is a deficient number, since it is larger than the sum of its proper divisors (1).

21189977 is an equidigital number, since it uses as much as digits as its factorization.

21189977 is an evil number, because the sum of its binary digits is even.

The product of its digits is 63504, while the sum is 44.

The square root of 21189977 is about 4603.2572163632. The cubic root of 21189977 is about 276.7218771770.

The spelling of 21189977 in words is "twenty-one million, one hundred eighty-nine thousand, nine hundred seventy-seven".