21734639 has 4 divisors (see below), whose sum is σ = 21893424. Its totient is φ = 21575856.

The previous prime is 21734621. The next prime is 21734681. The reversal of 21734639 is 93643712.

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

It is not a de Polignac number, because 21734639 - 2¹² = 21730543 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21734599 and 21734608.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21734039) 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, 79187 + ... + 79460.

It is an arithmetic number, because the mean of its divisors is an integer number (5473356).

Almost surely, 2^21734639 is an apocalyptic number.

21734639 is a deficient number, since it is larger than the sum of its proper divisors (158785).

21734639 is a wasteful number, since it uses less digits than its factorization.

21734639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 158784.

The product of its digits is 27216, while the sum is 35.

The square root of 21734639 is about 4662.0423635999. The cubic root of 21734639 is about 279.0727789820.

The spelling of 21734639 in words is "twenty-one million, seven hundred thirty-four thousand, six hundred thirty-nine".