21578045237491 has 4 divisors (see below), whose sum is σ = 21587200116912. Its totient is φ = 21568890358072.

The previous prime is 21578045237473. The next prime is 21578045237533. The reversal of 21578045237491 is 19473254087512.

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

It is a cyclic number.

It is not a de Polignac number, because 21578045237491 - 2¹¹ = 21578045235443 is a prime.

It is a super-2 number, since 2×21578045237491² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21578045247491) 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, 4577436175 + ... + 4577440888.

It is an arithmetic number, because the mean of its divisors is an integer number (5396800029228).

Almost surely, 2^{21578045237491} is an apocalyptic number.

21578045237491 is a deficient number, since it is larger than the sum of its proper divisors (9154879421).

21578045237491 is an equidigital number, since it uses as much as digits as its factorization.

21578045237491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9154879420.

The product of its (nonzero) digits is 16934400, while the sum is 58.

The spelling of 21578045237491 in words is "twenty-one trillion, five hundred seventy-eight billion, forty-five million, two hundred thirty-seven thousand, four hundred ninety-one".