21515542 has 4 divisors (see below), whose sum is σ = 32273316. Its totient is φ = 10757770.

The previous prime is 21515521. The next prime is 21515551. The reversal of 21515542 is 24551512.

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, 5378884 + ... + 5378887.

It is an arithmetic number, because the mean of its divisors is an integer number (8068329).

Almost surely, 2^21515542 is an apocalyptic number.

21515542 is a deficient number, since it is larger than the sum of its proper divisors (10757774).

21515542 is a wasteful number, since it uses less digits than its factorization.

21515542 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10757773.

The product of its digits is 2000, while the sum is 25.

The square root of 21515542 is about 4638.4848819415. The cubic root of 21515542 is about 278.1318750478.

The spelling of 21515542 in words is "twenty-one million, five hundred fifteen thousand, five hundred forty-two".