21250531 has 16 divisors (see below), whose sum is σ = 23372800. Its totient is φ = 19245600.

The previous prime is 21250517. The next prime is 21250553. The reversal of 21250531 is 13505212.

It is a cyclic number.

It is not a de Polignac number, because 21250531 - 2⁵ = 21250499 is a prime.

It is a super-2 number, since 2×21250531² = 903170135563922, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (19).

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21250499 and 21250508.

It is not an unprimeable number, because it can be changed into a prime (21250511) 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, 64036 + ... + 64366.

It is an arithmetic number, because the mean of its divisors is an integer number (1460800).

Almost surely, 2^21250531 is an apocalyptic number.

21250531 is a deficient number, since it is larger than the sum of its proper divisors (2122269).

21250531 is a wasteful number, since it uses less digits than its factorization.

21250531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 490.

The product of its (nonzero) digits is 300, while the sum is 19.

The square root of 21250531 is about 4609.8298233232. The cubic root of 21250531 is about 276.9852199232.

Adding to 21250531 its reverse (13505212), we get a palindrome (34755743).

The spelling of 21250531 in words is "twenty-one million, two hundred fifty thousand, five hundred thirty-one".