21154797955 has 4 divisors (see below), whose sum is σ = 25385757552. Its totient is φ = 16923838360.

The previous prime is 21154797919. The next prime is 21154797959. The reversal of 21154797955 is 55979745112.

It is a semiprime because it is the product of two primes.

It is a de Polignac number, because none of the positive numbers 2^k-21154797955 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21154797896 and 21154797905.

It is not an unprimeable number, because it can be changed into a prime (21154797959) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2115479791 + ... + 2115479800.

It is an arithmetic number, because the mean of its divisors is an integer number (6346439388).

Almost surely, 2^21154797955 is an apocalyptic number.

21154797955 is a deficient number, since it is larger than the sum of its proper divisors (4230959597).

21154797955 is an equidigital number, since it uses as much as digits as its factorization.

21154797955 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4230959596.

The product of its digits is 3969000, while the sum is 55.

The spelling of 21154797955 in words is "twenty-one billion, one hundred fifty-four million, seven hundred ninety-seven thousand, nine hundred fifty-five".