21734781 has 4 divisors (see below), whose sum is σ = 28979712. Its totient is φ = 14489852.

The previous prime is 21734777. The next prime is 21734827. The reversal of 21734781 is 18743712.

It is a happy number.

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 21734781 - 2² = 21734777 is a prime.

It is a super-2 number, since 2×21734781² = 944801410235922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21734711) 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, 3622461 + ... + 3622466.

It is an arithmetic number, because the mean of its divisors is an integer number (7244928).

Almost surely, 2^21734781 is an apocalyptic number.

It is an amenable number.

21734781 is a deficient number, since it is larger than the sum of its proper divisors (7244931).

21734781 is an equidigital number, since it uses as much as digits as its factorization.

21734781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7244930.

The product of its digits is 9408, while the sum is 33.

The square root of 21734781 is about 4662.0575929519. The cubic root of 21734781 is about 279.0733867407.

The spelling of 21734781 in words is "twenty-one million, seven hundred thirty-four thousand, seven hundred eighty-one".