21154372091 has 2 divisors, whose sum is σ = 21154372092. Its totient is φ = 21154372090.

The previous prime is 21154372067. The next prime is 21154372097. The reversal of 21154372091 is 19027345112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21154372091 - 2²⁶ = 21087263227 is a prime.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (21154372097) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10577186045 + 10577186046.

It is an arithmetic number, because the mean of its divisors is an integer number (10577186046).

Almost surely, 2^21154372091 is an apocalyptic number.

21154372091 is a deficient number, since it is larger than the sum of its proper divisors (1).

21154372091 is an equidigital number, since it uses as much as digits as its factorization.

21154372091 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 15120, while the sum is 35.

The spelling of 21154372091 in words is "twenty-one billion, one hundred fifty-four million, three hundred seventy-two thousand, ninety-one".