21510042 has 16 divisors (see below), whose sum is σ = 43074720. Its totient is φ = 7160912.

The previous prime is 21510029. The next prime is 21510053. The reversal of 21510042 is 24001512.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4309 + ... + 7847.

It is an arithmetic number, because the mean of its divisors is an integer number (2692170).

Almost surely, 2^21510042 is an apocalyptic number.

21510042 is an abundant number, since it is smaller than the sum of its proper divisors (21564678).

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

21510042 is a wasteful number, since it uses less digits than its factorization.

21510042 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4557.

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

The square root of 21510042 is about 4637.8919780435. The cubic root of 21510042 is about 278.1081734886.

Adding to 21510042 its reverse (24001512), we get a palindrome (45511554).

The spelling of 21510042 in words is "twenty-one million, five hundred ten thousand, forty-two".