21257799981 has 8 divisors (see below), whose sum is σ = 30920436384. Its totient is φ = 12883515120.

The previous prime is 21257799931. The next prime is 21257799989. The reversal of 21257799981 is 18999775212.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21257799981 - 2¹¹ = 21257797933 is a prime.

It is a super-2 number, since 2×21257799981² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21257799989) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 322087846 + ... + 322087911.

It is an arithmetic number, because the mean of its divisors is an integer number (3865054548).

Almost surely, 2^21257799981 is an apocalyptic number.

It is an amenable number.

21257799981 is a deficient number, since it is larger than the sum of its proper divisors (9662636403).

21257799981 is a wasteful number, since it uses less digits than its factorization.

21257799981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 644175771.

The product of its digits is 5715360, while the sum is 60.

The spelling of 21257799981 in words is "twenty-one billion, two hundred fifty-seven million, seven hundred ninety-nine thousand, nine hundred eighty-one".