21671351 has 16 divisors (see below), whose sum is σ = 23990400. Its totient is φ = 19454688.

The previous prime is 21671347. The next prime is 21671357. The reversal of 21671351 is 15317612.

It is a cyclic number.

It is not a de Polignac number, because 21671351 - 2² = 21671347 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21671351.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21671357) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 120980 + ... + 121158.

It is an arithmetic number, because the mean of its divisors is an integer number (1499400).

Almost surely, 2^21671351 is an apocalyptic number.

21671351 is a deficient number, since it is larger than the sum of its proper divisors (2319049).

21671351 is a wasteful number, since it uses less digits than its factorization.

21671351 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 398.

The product of its digits is 1260, while the sum is 26.

The square root of 21671351 is about 4655.2498321787. The cubic root of 21671351 is about 278.8016429886.

Adding to 21671351 its reverse (15317612), we get a palindrome (36988963).

It can be divided in two parts, 21671 and 351, that added together give a palindrome (22022).

The spelling of 21671351 in words is "twenty-one million, six hundred seventy-one thousand, three hundred fifty-one".