21431431 has 8 divisors (see below), whose sum is σ = 24554880. Its totient is φ = 18323448.

The previous prime is 21431401. The next prime is 21431489. The reversal of 21431431 is 13413412.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21431431 - 2⁷ = 21431303 is a prime.

It is a super-2 number, since 2×21431431² = 918612469415522, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21431399 and 21431408.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21431401) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 721 + ... + 6586.

It is an arithmetic number, because the mean of its divisors is an integer number (3069360).

Almost surely, 2^21431431 is an apocalyptic number.

21431431 is a deficient number, since it is larger than the sum of its proper divisors (3123449).

21431431 is an equidigital number, since it uses as much as digits as its factorization.

21431431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7733.

The product of its digits is 288, while the sum is 19.

The square root of 21431431 is about 4629.4093575747. The cubic root of 21431431 is about 277.7689668257.

Adding to 21431431 its reverse (13413412), we get a palindrome (34844843).

The spelling of 21431431 in words is "twenty-one million, four hundred thirty-one thousand, four hundred thirty-one".