21529421 has 4 divisors (see below), whose sum is σ = 21699072. Its totient is φ = 21359772.

The previous prime is 21529411. The next prime is 21529423. The reversal of 21529421 is 12492512.

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.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21529421 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 (21529423) 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, 84635 + ... + 84888.

It is an arithmetic number, because the mean of its divisors is an integer number (5424768).

Almost surely, 2^21529421 is an apocalyptic number.

It is an amenable number.

21529421 is a deficient number, since it is larger than the sum of its proper divisors (169651).

21529421 is a wasteful number, since it uses less digits than its factorization.

21529421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 169650.

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

The square root of 21529421 is about 4639.9807111668. The cubic root of 21529421 is about 278.1916669037.

The spelling of 21529421 in words is "twenty-one million, five hundred twenty-nine thousand, four hundred twenty-one".