21311421 has 16 divisors (see below), whose sum is σ = 30386304. Its totient is φ = 13238784.

The previous prime is 21311417. The next prime is 21311429. The reversal of 21311421 is 12411312.

It is not a de Polignac number, because 21311421 - 2² = 21311417 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21311421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21311429) 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, 3225 + ... + 7281.

It is an arithmetic number, because the mean of its divisors is an integer number (1899144).

Almost surely, 2^21311421 is an apocalyptic number.

It is an amenable number.

21311421 is a deficient number, since it is larger than the sum of its proper divisors (9074883).

21311421 is a wasteful number, since it uses less digits than its factorization.

21311421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4180.

The product of its digits is 48, while the sum is 15.

The square root of 21311421 is about 4616.4294644238. The cubic root of 21311421 is about 277.2495199392.

Adding to 21311421 its reverse (12411312), we get a palindrome (33722733).

The spelling of 21311421 in words is "twenty-one million, three hundred eleven thousand, four hundred twenty-one".