21422781 has 12 divisors (see below), whose sum is σ = 31406752. Its totient is φ = 14068296.

The previous prime is 21422743. The next prime is 21422783. The reversal of 21422781 is 18722412.

It is not a de Polignac number, because 21422781 - 2⁶ = 21422717 is a prime.

It is a super-2 number, since 2×21422781² = 917871091547922, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21422783) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 17161 + ... + 18366.

Almost surely, 2^21422781 is an apocalyptic number.

It is an amenable number.

21422781 is a deficient number, since it is larger than the sum of its proper divisors (9983971).

21422781 is a wasteful number, since it uses less digits than its factorization.

21422781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35600 (or 35597 counting only the distinct ones).

The product of its digits is 1792, while the sum is 27.

The square root of 21422781 is about 4628.4750188372. The cubic root of 21422781 is about 277.7315914262.

The spelling of 21422781 in words is "twenty-one million, four hundred twenty-two thousand, seven hundred eighty-one".