21979430 has 16 divisors (see below), whose sum is σ = 43159824. Its totient is φ = 7992480.

The previous prime is 21979429. The next prime is 21979439. The reversal of 21979430 is 3497912.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21979439) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 99797 + ... + 100016.

It is an arithmetic number, because the mean of its divisors is an integer number (2697489).

Almost surely, 2^21979430 is an apocalyptic number.

21979430 is a deficient number, since it is larger than the sum of its proper divisors (21180394).

21979430 is a wasteful number, since it uses less digits than its factorization.

21979430 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 199831.

The product of its (nonzero) digits is 13608, while the sum is 35.

The square root of 21979430 is about 4688.2224776561. Note that the first 3 decimals coincide. The cubic root of 21979430 is about 280.1165756077.

The spelling of 21979430 in words is "twenty-one million, nine hundred seventy-nine thousand, four hundred thirty".