21718461 has 4 divisors (see below), whose sum is σ = 28957952. Its totient is φ = 14478972.

The previous prime is 21718457. The next prime is 21718513. The reversal of 21718461 is 16481712.

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 not a de Polignac number, because 21718461 - 2² = 21718457 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21718421) 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, 3619741 + ... + 3619746.

It is an arithmetic number, because the mean of its divisors is an integer number (7239488).

Almost surely, 2^21718461 is an apocalyptic number.

It is an amenable number.

21718461 is a deficient number, since it is larger than the sum of its proper divisors (7239491).

21718461 is an equidigital number, since it uses as much as digits as its factorization.

21718461 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7239490.

The product of its digits is 2688, while the sum is 30.

The square root of 21718461 is about 4660.3069641387. The cubic root of 21718461 is about 279.0035199515.

The spelling of 21718461 in words is "twenty-one million, seven hundred eighteen thousand, four hundred sixty-one".