21001534 has 4 divisors (see below), whose sum is σ = 31502304. Its totient is φ = 10500766.

The previous prime is 21001531. The next prime is 21001549. The reversal of 21001534 is 43510012.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5250382 + ... + 5250385.

It is an arithmetic number, because the mean of its divisors is an integer number (7875576).

Almost surely, 2^21001534 is an apocalyptic number.

21001534 is a deficient number, since it is larger than the sum of its proper divisors (10500770).

21001534 is a wasteful number, since it uses less digits than its factorization.

21001534 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10500769.

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 21001534 is about 4582.7430650212. The cubic root of 21001534 is about 275.8991352360.

Adding to 21001534 its reverse (43510012), we get a palindrome (64511546).

The spelling of 21001534 in words is "twenty-one million, one thousand, five hundred thirty-four".