21739649 has 4 divisors (see below), whose sum is σ = 22440960. Its totient is φ = 21038340.

The previous prime is 21739643. The next prime is 21739661. The reversal of 21739649 is 94693712.

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 21739649 - 2¹⁶ = 21674113 is a prime.

It is a super-2 number, since 2×21739649² = 945224677286402, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21739643) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 350609 + ... + 350670.

It is an arithmetic number, because the mean of its divisors is an integer number (5610240).

Almost surely, 2^21739649 is an apocalyptic number.

It is an amenable number.

21739649 is a deficient number, since it is larger than the sum of its proper divisors (701311).

21739649 is an equidigital number, since it uses as much as digits as its factorization.

21739649 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 701310.

The product of its digits is 81648, while the sum is 41.

The square root of 21739649 is about 4662.5796507942. The cubic root of 21739649 is about 279.0942201357.

The spelling of 21739649 in words is "twenty-one million, seven hundred thirty-nine thousand, six hundred forty-nine".