21430551 has 4 divisors (see below), whose sum is σ = 28574072. Its totient is φ = 14287032.

The previous prime is 21430531. The next prime is 21430559. The reversal of 21430551 is 15503412.

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

It is not a de Polignac number, because 21430551 - 2¹¹ = 21428503 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21430559) 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, 3571756 + ... + 3571761.

It is an arithmetic number, because the mean of its divisors is an integer number (7143518).

Almost surely, 2^21430551 is an apocalyptic number.

21430551 is a deficient number, since it is larger than the sum of its proper divisors (7143521).

21430551 is an equidigital number, since it uses as much as digits as its factorization.

21430551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7143520.

The product of its (nonzero) digits is 600, while the sum is 21.

The square root of 21430551 is about 4629.3143120769. The cubic root of 21430551 is about 277.7651649325.

Adding to 21430551 its reverse (15503412), we get a palindrome (36933963).

The spelling of 21430551 in words is "twenty-one million, four hundred thirty thousand, five hundred fifty-one".