21540501 has 6 divisors (see below), whose sum is σ = 31114070. Its totient is φ = 14360328.

The previous prime is 21540473. The next prime is 21540529. The reversal of 21540501 is 10504512.

It is an interprime number because it is at equal distance from previous prime (21540473) and next prime (21540529).

It can be written as a sum of positive squares in only one way, i.e., 21399876 + 140625 = 4626^2 + 375^2 .

It is not a de Polignac number, because 21540501 - 2⁶ = 21540437 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 (21540551) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1196686 + ... + 1196703.

Almost surely, 2^21540501 is an apocalyptic number.

It is an amenable number.

21540501 is a deficient number, since it is larger than the sum of its proper divisors (9573569).

21540501 is a wasteful number, since it uses less digits than its factorization.

21540501 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2393395 (or 2393392 counting only the distinct ones).

The product of its (nonzero) digits is 200, while the sum is 18.

The square root of 21540501 is about 4641.1745280694. The cubic root of 21540501 is about 278.2393819978.

The spelling of 21540501 in words is "twenty-one million, five hundred forty thousand, five hundred one".