21305377 has 4 divisors (see below), whose sum is σ = 21881236. Its totient is φ = 20729520.

The previous prime is 21305357. The next prime is 21305399. The reversal of 21305377 is 77350312.

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 10342656 + 10962721 = 3216^2 + 3311^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21305377 is a prime.

It is a super-2 number, since 2×21305377² = 907838178224258, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21305357) 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, 287874 + ... + 287947.

It is an arithmetic number, because the mean of its divisors is an integer number (5470309).

Almost surely, 2^21305377 is an apocalyptic number.

It is an amenable number.

21305377 is a deficient number, since it is larger than the sum of its proper divisors (575859).

21305377 is an equidigital number, since it uses as much as digits as its factorization.

21305377 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 575858.

The product of its (nonzero) digits is 4410, while the sum is 28.

The square root of 21305377 is about 4615.7747995326. The cubic root of 21305377 is about 277.2233077885.

Adding to 21305377 its reverse (77350312), we get a palindrome (98655689).

The spelling of 21305377 in words is "twenty-one million, three hundred five thousand, three hundred seventy-seven".