21748978091 has 2 divisors, whose sum is σ = 21748978092. Its totient is φ = 21748978090.

The previous prime is 21748978079. The next prime is 21748978133. The reversal of 21748978091 is 19087984712.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21748978091 is a prime.

It is not a weakly prime, because it can be changed into another prime (21748978021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10874489045 + 10874489046.

It is an arithmetic number, because the mean of its divisors is an integer number (10874489046).

Almost surely, 2^21748978091 is an apocalyptic number.

21748978091 is a deficient number, since it is larger than the sum of its proper divisors (1).

21748978091 is an equidigital number, since it uses as much as digits as its factorization.

21748978091 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2032128, while the sum is 56.

The spelling of 21748978091 in words is "twenty-one billion, seven hundred forty-eight million, nine hundred seventy-eight thousand, ninety-one".