21521429 has 4 divisors (see below), whose sum is σ = 21532800. Its totient is φ = 21510060.

The previous prime is 21521419. The next prime is 21521431. The reversal of 21521429 is 92412512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21521429 - 2⁴ = 21521413 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21521398 and 21521407.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21521419) 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, 2087 + ... + 6884.

It is an arithmetic number, because the mean of its divisors is an integer number (5383200).

Almost surely, 2^21521429 is an apocalyptic number.

It is an amenable number.

21521429 is a deficient number, since it is larger than the sum of its proper divisors (11371).

21521429 is an equidigital number, since it uses as much as digits as its factorization.

21521429 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11370.

The product of its digits is 1440, while the sum is 26.

The square root of 21521429 is about 4639.1194207522. The cubic root of 21521429 is about 278.1572398598.

The spelling of 21521429 in words is "twenty-one million, five hundred twenty-one thousand, four hundred twenty-nine".