21305638197 has 32 divisors (see below), whose sum is σ = 32333506560. Its totient is φ = 13859279280.

The previous prime is 21305638187. The next prime is 21305638261. The reversal of 21305638197 is 79183650312.

21305638197 is a `hidden beast` number, since 2 + 1 + 3 + 0 + 5 + 638 + 1 + 9 + 7 = 666.

It is not a de Polignac number, because 21305638197 - 2¹² = 21305634101 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21305638147) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 394678 + ... + 445400.

It is an arithmetic number, because the mean of its divisors is an integer number (1010422080).

Almost surely, 2^21305638197 is an apocalyptic number.

21305638197 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21305638197 is a deficient number, since it is larger than the sum of its proper divisors (11027868363).

21305638197 is a wasteful number, since it uses less digits than its factorization.

21305638197 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51110 (or 51104 counting only the distinct ones).

The product of its (nonzero) digits is 272160, while the sum is 45.

The spelling of 21305638197 in words is "twenty-one billion, three hundred five million, six hundred thirty-eight thousand, one hundred ninety-seven".