21536431 has 6 divisors (see below), whose sum is σ = 25052640. Its totient is φ = 18459756.

The previous prime is 21536419. The next prime is 21536447. The reversal of 21536431 is 13463512.

It is not a de Polignac number, because 21536431 - 2¹⁷ = 21405359 is a prime.

It is a super-2 number, since 2×21536431² = 927635720435522, 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 = 21536396 and 21536405.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21536401) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 219711 + ... + 219808.

It is an arithmetic number, because the mean of its divisors is an integer number (4175440).

Almost surely, 2^21536431 is an apocalyptic number.

21536431 is a deficient number, since it is larger than the sum of its proper divisors (3516209).

21536431 is an equidigital number, since it uses as much as digits as its factorization.

21536431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 439533 (or 439526 counting only the distinct ones).

The product of its digits is 2160, while the sum is 25.

The square root of 21536431 is about 4640.7360407591. The cubic root of 21536431 is about 278.2218567847.

Adding to 21536431 its reverse (13463512), we get a palindrome (34999943).

The spelling of 21536431 in words is "twenty-one million, five hundred thirty-six thousand, four hundred thirty-one".