21042377 has 4 divisors (see below), whose sum is σ = 21387396. Its totient is φ = 20697360.

The previous prime is 21042353. The next prime is 21042383. The reversal of 21042377 is 77324012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 9339136 + 11703241 = 3056^2 + 3421^2 .

It is a cyclic number.

It is not a de Polignac number, because 21042377 - 2¹⁰ = 21041353 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21042317) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 172418 + ... + 172539.

It is an arithmetic number, because the mean of its divisors is an integer number (5346849).

Almost surely, 2^21042377 is an apocalyptic number.

It is an amenable number.

21042377 is a deficient number, since it is larger than the sum of its proper divisors (345019).

21042377 is an equidigital number, since it uses as much as digits as its factorization.

21042377 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 345018.

The product of its (nonzero) digits is 2352, while the sum is 26.

The square root of 21042377 is about 4587.1970744672. The cubic root of 21042377 is about 276.0778722015.

Adding to 21042377 its reverse (77324012), we get a palindrome (98366389).

The spelling of 21042377 in words is "twenty-one million, forty-two thousand, three hundred seventy-seven".