21739399091 has 2 divisors, whose sum is σ = 21739399092. Its totient is φ = 21739399090.

The previous prime is 21739399067. The next prime is 21739399139. The reversal of 21739399091 is 19099393712.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21739399091 - 2³⁰ = 20665657267 is a prime.

It is not a weakly prime, because it can be changed into another prime (21739390091) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10869699545 + 10869699546.

It is an arithmetic number, because the mean of its divisors is an integer number (10869699546).

Almost surely, 2^21739399091 is an apocalyptic number.

21739399091 is a deficient number, since it is larger than the sum of its proper divisors (1).

21739399091 is an equidigital number, since it uses as much as digits as its factorization.

21739399091 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 826686, while the sum is 53.

The spelling of 21739399091 in words is "twenty-one billion, seven hundred thirty-nine million, three hundred ninety-nine thousand, ninety-one".