21023902 has 4 divisors (see below), whose sum is σ = 31535856. Its totient is φ = 10511950.

The previous prime is 21023887. The next prime is 21023923. The reversal of 21023902 is 20932012.

It is a happy number.

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

It is a self number, because there is not a number n which added to its sum of digits gives 21023902.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5255974 + ... + 5255977.

It is an arithmetic number, because the mean of its divisors is an integer number (7883964).

Almost surely, 2^21023902 is an apocalyptic number.

21023902 is a deficient number, since it is larger than the sum of its proper divisors (10511954).

21023902 is a wasteful number, since it uses less digits than its factorization.

21023902 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10511953.

The product of its (nonzero) digits is 216, while the sum is 19.

The square root of 21023902 is about 4585.1828753061. The cubic root of 21023902 is about 275.9970506581.

Adding to 21023902 its reverse (20932012), we get a palindrome (41955914).

The spelling of 21023902 in words is "twenty-one million, twenty-three thousand, nine hundred two".