21361431 has 32 divisors (see below), whose sum is σ = 35338240. Its totient is φ = 11243232.

The previous prime is 21361427. The next prime is 21361447. The reversal of 21361431 is 13416312.

It is not a de Polignac number, because 21361431 - 2² = 21361427 is a prime.

It is a super-2 number, since 2×21361431² = 912621468735522, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a junction number, because it is equal to n+sod(n) for n = 21361398 and 21361407.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21361421) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 45906 + ... + 46368.

It is an arithmetic number, because the mean of its divisors is an integer number (1104320).

Almost surely, 2^21361431 is an apocalyptic number.

21361431 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21361431 is a deficient number, since it is larger than the sum of its proper divisors (13976809).

21361431 is an equidigital number, since it uses as much as digits as its factorization.

21361431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 512 (or 486 counting only the distinct ones).

The product of its digits is 432, while the sum is 21.

The square root of 21361431 is about 4621.8428142896. The cubic root of 21361431 is about 277.4662177852.

Adding to 21361431 its reverse (13416312), we get a palindrome (34777743).

The spelling of 21361431 in words is "twenty-one million, three hundred sixty-one thousand, four hundred thirty-one".