21542506 has 4 divisors (see below), whose sum is σ = 32313762. Its totient is φ = 10771252.

The previous prime is 21542483. The next prime is 21542537. The reversal of 21542506 is 60524512.

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

It can be written as a sum of positive squares in only one way, i.e., 20657025 + 885481 = 4545^2 + 941^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5385625 + ... + 5385628.

Almost surely, 2^21542506 is an apocalyptic number.

21542506 is a deficient number, since it is larger than the sum of its proper divisors (10771256).

21542506 is a wasteful number, since it uses less digits than its factorization.

21542506 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10771255.

The product of its (nonzero) digits is 2400, while the sum is 25.

The square root of 21542506 is about 4641.3905244011. The cubic root of 21542506 is about 278.2480146143.

The spelling of 21542506 in words is "twenty-one million, five hundred forty-two thousand, five hundred six".