21521534 has 4 divisors (see below), whose sum is σ = 32282304. Its totient is φ = 10760766.

The previous prime is 21521527. The next prime is 21521557. The reversal of 21521534 is 43512512.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5380382 + ... + 5380385.

It is an arithmetic number, because the mean of its divisors is an integer number (8070576).

Almost surely, 2^21521534 is an apocalyptic number.

21521534 is a deficient number, since it is larger than the sum of its proper divisors (10760770).

21521534 is a wasteful number, since it uses less digits than its factorization.

21521534 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10760769.

The product of its digits is 1200, while the sum is 23.

The square root of 21521534 is about 4639.1307375412. The cubic root of 21521534 is about 278.1576922224.

The spelling of 21521534 in words is "twenty-one million, five hundred twenty-one thousand, five hundred thirty-four".