21001542 has 16 divisors (see below), whose sum is σ = 42051312. Its totient is φ = 6992480.

The previous prime is 21001531. The next prime is 21001549. The reversal of 21001542 is 24510012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001549) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6292 + ... + 9032.

It is an arithmetic number, because the mean of its divisors is an integer number (2628207).

Almost surely, 2^21001542 is an apocalyptic number.

21001542 is an abundant number, since it is smaller than the sum of its proper divisors (21049770).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21001542 is a wasteful number, since it uses less digits than its factorization.

21001542 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4023.

The product of its (nonzero) digits is 80, while the sum is 15.

The square root of 21001542 is about 4582.7439378608. The cubic root of 21001542 is about 275.8991702682.

Adding to 21001542 its reverse (24510012), we get a palindrome (45511554).

The spelling of 21001542 in words is "twenty-one million, one thousand, five hundred forty-two".