21042877 has 2 divisors, whose sum is σ = 21042878. Its totient is φ = 21042876.

The previous prime is 21042863. The next prime is 21042883. The reversal of 21042877 is 77824012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19263321 + 1779556 = 4389^2 + 1334^2 .

It is a cyclic number.

It is not a de Polignac number, because 21042877 - 2²³ = 12654269 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21042577) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10521438 + 10521439.

It is an arithmetic number, because the mean of its divisors is an integer number (10521439).

Almost surely, 2^21042877 is an apocalyptic number.

It is an amenable number.

21042877 is a deficient number, since it is larger than the sum of its proper divisors (1).

21042877 is an equidigital number, since it uses as much as digits as its factorization.

21042877 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6272, while the sum is 31.

The square root of 21042877 is about 4587.2515736550. The cubic root of 21042877 is about 276.0800588658.

Adding to 21042877 its reverse (77824012), we get a palindrome (98866889).

The spelling of 21042877 in words is "twenty-one million, forty-two thousand, eight hundred seventy-seven".