21302421 has 32 divisors (see below), whose sum is σ = 33619968. Its totient is φ = 11746560.

The previous prime is 21302419. The next prime is 21302447. The reversal of 21302421 is 12420312.

It is not a de Polignac number, because 21302421 - 2¹ = 21302419 is a prime.

It is a super-2 number, since 2×21302421² = 907586280922482, which contains 22 as substring.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21302421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21302221) 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, 111436 + ... + 111626.

It is an arithmetic number, because the mean of its divisors is an integer number (1050624).

Almost surely, 2^21302421 is an apocalyptic number.

21302421 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21302421 is a deficient number, since it is larger than the sum of its proper divisors (12317547).

21302421 is a wasteful number, since it uses less digits than its factorization.

21302421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 361.

The product of its (nonzero) digits is 96, while the sum is 15.

The square root of 21302421 is about 4615.4545821620. The cubic root of 21302421 is about 277.2104861426.

Adding to 21302421 its reverse (12420312), we get a palindrome (33722733).

The spelling of 21302421 in words is "twenty-one million, three hundred two thousand, four hundred twenty-one".