21018377 has 4 divisors (see below), whose sum is σ = 21106560. Its totient is φ = 20930196.

The previous prime is 21018323. The next prime is 21018397. The reversal of 21018377 is 77381012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21018377 - 2¹⁸ = 20756233 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21018317) 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, 43733 + ... + 44210.

It is an arithmetic number, because the mean of its divisors is an integer number (5276640).

Almost surely, 2^21018377 is an apocalyptic number.

It is an amenable number.

21018377 is a deficient number, since it is larger than the sum of its proper divisors (88183).

21018377 is an equidigital number, since it uses as much as digits as its factorization.

21018377 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 88182.

The product of its (nonzero) digits is 2352, while the sum is 29.

The square root of 21018377 is about 4584.5803515698. The cubic root of 21018377 is about 275.9728715547.

Adding to 21018377 its reverse (77381012), we get a palindrome (98399389).

The spelling of 21018377 in words is "twenty-one million, eighteen thousand, three hundred seventy-seven".