20979543 has 16 divisors (see below), whose sum is σ = 30541280. Its totient is φ = 12731904.

The previous prime is 20979533. The next prime is 20979551. The reversal of 20979543 is 34597902.

It is not a de Polignac number, because 20979543 - 2¹⁸ = 20717399 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20979533) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 838 + ... + 6531.

It is an arithmetic number, because the mean of its divisors is an integer number (1908830).

Almost surely, 2^20979543 is an apocalyptic number.

20979543 is a deficient number, since it is larger than the sum of its proper divisors (9561737).

20979543 is a wasteful number, since it uses less digits than its factorization.

20979543 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7458.

The product of its (nonzero) digits is 68040, while the sum is 39.

The square root of 20979543 is about 4580.3431094188. The cubic root of 20979543 is about 275.8028023231.

The spelling of 20979543 in words is "twenty million, nine hundred seventy-nine thousand, five hundred forty-three".