21396431 has 8 divisors (see below), whose sum is σ = 24610080. Its totient is φ = 18222048.

The previous prime is 21396379. The next prime is 21396449. The reversal of 21396431 is 13469312.

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

It is not a de Polignac number, because 21396431 - 2¹⁸ = 21134287 is a prime.

It is a super-2 number, since 2×21396431² = 915614519075522, which contains 22 as substring.

It is a Duffinian number.

It is a plaindrome in base 16.

It is a junction number, because it is equal to n+sod(n) for n = 21396394 and 21396403.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21396481) 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, 8636 + ... + 10833.

It is an arithmetic number, because the mean of its divisors is an integer number (3076260).

Almost surely, 2^21396431 is an apocalyptic number.

21396431 is a deficient number, since it is larger than the sum of its proper divisors (3213649).

21396431 is a wasteful number, since it uses less digits than its factorization.

21396431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19633.

The product of its digits is 3888, while the sum is 29.

The square root of 21396431 is about 4625.6276330894. The cubic root of 21396431 is about 277.6176748443.

The spelling of 21396431 in words is "twenty-one million, three hundred ninety-six thousand, four hundred thirty-one".