21350531 has 4 divisors (see below), whose sum is σ = 21359952. Its totient is φ = 21341112.

The previous prime is 21350501. The next prime is 21350533. The reversal of 21350531 is 13505312.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21350531 is a prime.

It is a super-2 number, since 2×21350531² = 911690347963922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21350533) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 986 + ... + 6608.

It is an arithmetic number, because the mean of its divisors is an integer number (5339988).

Almost surely, 2^21350531 is an apocalyptic number.

21350531 is a deficient number, since it is larger than the sum of its proper divisors (9421).

21350531 is an equidigital number, since it uses as much as digits as its factorization.

21350531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9420.

The product of its (nonzero) digits is 450, while the sum is 20.

The square root of 21350531 is about 4620.6634804971. The cubic root of 21350531 is about 277.4190159485.

Adding to 21350531 its reverse (13505312), we get a palindrome (34855843).

The spelling of 21350531 in words is "twenty-one million, three hundred fifty thousand, five hundred thirty-one".