21506642979 has 8 divisors (see below), whose sum is σ = 28678307520. Its totient is φ = 14336370216.

The previous prime is 21506642939. The next prime is 21506643013. The reversal of 21506642979 is 97924660512.

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

It is not a de Polignac number, because 21506642979 - 2⁷ = 21506642851 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21506642939) 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, 311337 + ... + 374090.

It is an arithmetic number, because the mean of its divisors is an integer number (3584788440).

Almost surely, 2^21506642979 is an apocalyptic number.

21506642979 is a deficient number, since it is larger than the sum of its proper divisors (7171664541).

21506642979 is a wasteful number, since it uses less digits than its factorization.

21506642979 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 695889.

The product of its (nonzero) digits is 1632960, while the sum is 51.

The spelling of 21506642979 in words is "twenty-one billion, five hundred six million, six hundred forty-two thousand, nine hundred seventy-nine".