21685277 has 2 divisors, whose sum is σ = 21685278. Its totient is φ = 21685276.

The previous prime is 21685271. The next prime is 21685309. The reversal of 21685277 is 77258612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17131321 + 4553956 = 4139^2 + 2134^2 .

It is a cyclic number.

It is not a de Polignac number, because 21685277 - 2²⁰ = 20636701 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21685277.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21685271) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10842638 + 10842639.

It is an arithmetic number, because the mean of its divisors is an integer number (10842639).

Almost surely, 2^21685277 is an apocalyptic number.

It is an amenable number.

21685277 is a deficient number, since it is larger than the sum of its proper divisors (1).

21685277 is an equidigital number, since it uses as much as digits as its factorization.

21685277 is an evil number, because the sum of its binary digits is even.

The product of its digits is 47040, while the sum is 38.

The square root of 21685277 is about 4656.7453226476. The cubic root of 21685277 is about 278.8613494697.

The spelling of 21685277 in words is "twenty-one million, six hundred eighty-five thousand, two hundred seventy-seven".