21553739 has 8 divisors (see below), whose sum is σ = 22862160. Its totient is φ = 20249856.

The previous prime is 21553717. The next prime is 21553787. The reversal of 21553739 is 93735512.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21553739 - 2²⁴ = 4776523 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21553699 and 21553708.

It is not an unprimeable number, because it can be changed into a prime (21553789) 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 7 ways as a sum of consecutive naturals, for example, 18527 + ... + 19655.

It is an arithmetic number, because the mean of its divisors is an integer number (2857770).

Almost surely, 2^21553739 is an apocalyptic number.

21553739 is a deficient number, since it is larger than the sum of its proper divisors (1308421).

21553739 is a wasteful number, since it uses less digits than its factorization.

21553739 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2269.

The product of its digits is 28350, while the sum is 35.

The square root of 21553739 is about 4642.6004566407. The cubic root of 21553739 is about 278.2963688904.

The spelling of 21553739 in words is "twenty-one million, five hundred fifty-three thousand, seven hundred thirty-nine".