21435381 has 16 divisors (see below), whose sum is σ = 34643520. Its totient is φ = 12990960.

The previous prime is 21435347. The next prime is 21435389. The reversal of 21435381 is 18353412.

It is a happy number.

It is a de Polignac number, because none of the positive numbers 2^k-21435381 is a prime.

It is a super-2 number, since 2×21435381² = 918951117230322, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21435389) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 35790 + ... + 36383.

It is an arithmetic number, because the mean of its divisors is an integer number (2165220).

Almost surely, 2^21435381 is an apocalyptic number.

It is an amenable number.

21435381 is a deficient number, since it is larger than the sum of its proper divisors (13208139).

21435381 is a wasteful number, since it uses less digits than its factorization.

21435381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72193 (or 72187 counting only the distinct ones).

The product of its digits is 2880, while the sum is 27.

The square root of 21435381 is about 4629.8359582171. The cubic root of 21435381 is about 277.7860308600.

Adding to 21435381 its reverse (18353412), we get a palindrome (39788793).

The spelling of 21435381 in words is "twenty-one million, four hundred thirty-five thousand, three hundred eighty-one".