21250931 has 4 divisors (see below), whose sum is σ = 22885632. Its totient is φ = 19616232.

The previous prime is 21250877. The next prime is 21250961. The reversal of 21250931 is 13905212.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21250931 is a prime.

It is a super-2 number, since 2×21250931² = 903204136733522, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21250897 and 21250906.

It is not an unprimeable number, because it can be changed into a prime (21250961) 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 in 3 ways as a sum of consecutive naturals, for example, 817331 + ... + 817356.

It is an arithmetic number, because the mean of its divisors is an integer number (5721408).

Almost surely, 2^21250931 is an apocalyptic number.

21250931 is a deficient number, since it is larger than the sum of its proper divisors (1634701).

21250931 is a wasteful number, since it uses less digits than its factorization.

21250931 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1634700.

The product of its (nonzero) digits is 540, while the sum is 23.

The square root of 21250931 is about 4609.8732086685. The cubic root of 21250931 is about 276.9869578154.

The spelling of 21250931 in words is "twenty-one million, two hundred fifty thousand, nine hundred thirty-one".