21056655197 has 4 divisors (see below), whose sum is σ = 21057848736. Its totient is φ = 21055461660.

The previous prime is 21056655187. The next prime is 21056655223. The reversal of 21056655197 is 79155665012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21056655197 - 2¹² = 21056651101 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21056655127) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 569903 + ... + 605724.

It is an arithmetic number, because the mean of its divisors is an integer number (5264462184).

Almost surely, 2^21056655197 is an apocalyptic number.

It is an amenable number.

21056655197 is a deficient number, since it is larger than the sum of its proper divisors (1193539).

21056655197 is a wasteful number, since it uses less digits than its factorization.

21056655197 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1193538.

The product of its (nonzero) digits is 567000, while the sum is 47.

The spelling of 21056655197 in words is "twenty-one billion, fifty-six million, six hundred fifty-five thousand, one hundred ninety-seven".