21704451 has 4 divisors (see below), whose sum is σ = 28939272. Its totient is φ = 14469632.

The previous prime is 21704447. The next prime is 21704467. The reversal of 21704451 is 15440712.

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

It is a cyclic number.

It is not a de Polignac number, because 21704451 - 2² = 21704447 is a prime.

It is a super-2 number, since 2×21704451² = 942166386422802, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21704411) 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, 3617406 + ... + 3617411.

It is an arithmetic number, because the mean of its divisors is an integer number (7234818).

Almost surely, 2^21704451 is an apocalyptic number.

21704451 is a deficient number, since it is larger than the sum of its proper divisors (7234821).

21704451 is an equidigital number, since it uses as much as digits as its factorization.

21704451 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7234820.

The product of its (nonzero) digits is 1120, while the sum is 24.

The square root of 21704451 is about 4658.8036017845. The cubic root of 21704451 is about 278.9435144702.

It can be divided in two parts, 21704 and 451, that added together give a triangular number (22155 = T₂₁₀).

The spelling of 21704451 in words is "twenty-one million, seven hundred four thousand, four hundred fifty-one".