21431026 has 4 divisors (see below), whose sum is σ = 32146542. Its totient is φ = 10715512.

The previous prime is 21431023. The next prime is 21431057. The reversal of 21431026 is 62013412.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 21390625 + 40401 = 4625^2 + 201^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21430994 and 21431012.

It is not an unprimeable number, because it can be changed into a prime (21431023) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5357755 + ... + 5357758.

Almost surely, 2^21431026 is an apocalyptic number.

21431026 is the 2475-th centered heptagonal number.

21431026 is a deficient number, since it is larger than the sum of its proper divisors (10715516).

21431026 is a wasteful number, since it uses less digits than its factorization.

21431026 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10715515.

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

The square root of 21431026 is about 4629.3656152868. The cubic root of 21431026 is about 277.7672171037.

Adding to 21431026 its reverse (62013412), we get a palindrome (83444438).

The spelling of 21431026 in words is "twenty-one million, four hundred thirty-one thousand, twenty-six".