21552431 has 4 divisors (see below), whose sum is σ = 21628872. Its totient is φ = 21475992.

The previous prime is 21552383. The next prime is 21552437. The reversal of 21552431 is 13425512.

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

It is a cyclic number.

It is not a de Polignac number, because 21552431 - 2¹⁰ = 21551407 is a prime.

It is a super-2 number, since 2×21552431² = 929014564019522, 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 = 21552397 and 21552406.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21552437) 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, 37796 + ... + 38361.

It is an arithmetic number, because the mean of its divisors is an integer number (5407218).

Almost surely, 2^21552431 is an apocalyptic number.

21552431 is a deficient number, since it is larger than the sum of its proper divisors (76441).

21552431 is an equidigital number, since it uses as much as digits as its factorization.

21552431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 76440.

The product of its digits is 1200, while the sum is 23.

The square root of 21552431 is about 4642.4595851768. The cubic root of 21552431 is about 278.2907392560.

Adding to 21552431 its reverse (13425512), we get a palindrome (34977943).

The spelling of 21552431 in words is "twenty-one million, five hundred fifty-two thousand, four hundred thirty-one".