21445287981 has 32 divisors (see below), whose sum is σ = 32532917760. Its totient is φ = 12470889984.

The previous prime is 21445287979. The next prime is 21445287989. The reversal of 21445287981 is 18978254412.

It is not a de Polignac number, because 21445287981 - 2¹ = 21445287979 is a prime.

It is a super-2 number, since 2×21445287981² (a number of 21 digits) contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21445287989) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 148560 + ... + 254873.

It is an arithmetic number, because the mean of its divisors is an integer number (1016653680).

Almost surely, 2^21445287981 is an apocalyptic number.

It is an amenable number.

21445287981 is a deficient number, since it is larger than the sum of its proper divisors (11087629779).

21445287981 is a wasteful number, since it uses less digits than its factorization.

21445287981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 403525.

The product of its digits is 1290240, while the sum is 51.

The spelling of 21445287981 in words is "twenty-one billion, four hundred forty-five million, two hundred eighty-seven thousand, nine hundred eighty-one".