21070904 has 8 divisors (see below), whose sum is σ = 39507960. Its totient is φ = 10535448.

The previous prime is 21070901. The next prime is 21070909. The reversal of 21070904 is 40907012.

It is a tau number, because it is divible by the number of its divisors (8).

It is a self number, because there is not a number n which added to its sum of digits gives 21070904.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21070901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1316924 + ... + 1316939.

It is an arithmetic number, because the mean of its divisors is an integer number (4938495).

Almost surely, 2^21070904 is an apocalyptic number.

It is an amenable number.

21070904 is a deficient number, since it is larger than the sum of its proper divisors (18437056).

21070904 is a wasteful number, since it uses less digits than its factorization.

21070904 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2633869 (or 2633865 counting only the distinct ones).

The product of its (nonzero) digits is 504, while the sum is 23.

The square root of 21070904 is about 4590.3054364606. The cubic root of 21070904 is about 276.2025747979.

Adding to 21070904 its reverse (40907012), we get a palindrome (61977916).

The spelling of 21070904 in words is "twenty-one million, seventy thousand, nine hundred four".