21891273849 has 27 divisors (see below), whose sum is σ = 31930839759. Its totient is φ = 14452439760.

The previous prime is 21891273823. The next prime is 21891273851. The reversal of 21891273849 is 94837219812.

The square root of 21891273849 is 147957.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 2564713449 + 19326560400 = 50643^2 + 139020^2 .

It is not a de Polignac number, because 21891273849 - 2⁷ = 21891273721 is a prime.

It is a super-2 number, since 2×21891273849² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21891273795 and 21891273804.

It is not an unprimeable number, because it can be changed into a prime (21891273889) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 66136614 + ... + 66136944.

Almost surely, 2^21891273849 is an apocalyptic number.

21891273849 is the 147957-th square number.

21891273849 is the 73979-th centered octagonal number.

It is an amenable number.

21891273849 is a deficient number, since it is larger than the sum of its proper divisors (10039565910).

21891273849 is an frugal number, since it uses more digits than its factorization.

21891273849 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 966 (or 483 counting only the distinct ones).

The product of its digits is 1741824, while the sum is 54.

The spelling of 21891273849 in words is "twenty-one billion, eight hundred ninety-one million, two hundred seventy-three thousand, eight hundred forty-nine".