21546251 has 4 divisors (see below), whose sum is σ = 21701400. Its totient is φ = 21391104.

The previous prime is 21546241. The next prime is 21546253. The reversal of 21546251 is 15264512.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21546251 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21546251.

It is not an unprimeable number, because it can be changed into a prime (21546253) 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, 77366 + ... + 77643.

It is an arithmetic number, because the mean of its divisors is an integer number (5425350).

Almost surely, 2^21546251 is an apocalyptic number.

21546251 is a deficient number, since it is larger than the sum of its proper divisors (155149).

21546251 is a wasteful number, since it uses less digits than its factorization.

21546251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 155148.

The product of its digits is 2400, while the sum is 26.

The square root of 21546251 is about 4641.7939420013. The cubic root of 21546251 is about 278.2641374436.

The spelling of 21546251 in words is "twenty-one million, five hundred forty-six thousand, two hundred fifty-one".