21254501 has 4 divisors (see below), whose sum is σ = 21269292. Its totient is φ = 21239712.

The previous prime is 21254491. The next prime is 21254567. The reversal of 21254501 is 10545212.

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

It can be written as a sum of positive squares in 2 ways, for example, as 13498276 + 7756225 = 3674^2 + 2785^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21254501 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21254581) 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, 4976 + ... + 8201.

It is an arithmetic number, because the mean of its divisors is an integer number (5317323).

Almost surely, 2^21254501 is an apocalyptic number.

It is an amenable number.

21254501 is a deficient number, since it is larger than the sum of its proper divisors (14791).

21254501 is a wasteful number, since it uses less digits than its factorization.

21254501 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14790.

The product of its (nonzero) digits is 400, while the sum is 20.

The square root of 21254501 is about 4610.2604047928. The cubic root of 21254501 is about 277.0024675370.

Adding to 21254501 its reverse (10545212), we get a palindrome (31799713).

The spelling of 21254501 in words is "twenty-one million, two hundred fifty-four thousand, five hundred one".