21542501 has 4 divisors (see below), whose sum is σ = 21582432. Its totient is φ = 21502572.

The previous prime is 21542483. The next prime is 21542537. The reversal of 21542501 is 10524512.

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 not a de Polignac number, because 21542501 - 2¹⁰ = 21541477 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21545501) 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, 19145 + ... + 20238.

It is an arithmetic number, because the mean of its divisors is an integer number (5395608).

Almost surely, 2^21542501 is an apocalyptic number.

It is an amenable number.

21542501 is a deficient number, since it is larger than the sum of its proper divisors (39931).

21542501 is an equidigital number, since it uses as much as digits as its factorization.

21542501 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39930.

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

The square root of 21542501 is about 4641.3899857693. The cubic root of 21542501 is about 278.2479930873.

The spelling of 21542501 in words is "twenty-one million, five hundred forty-two thousand, five hundred one".