21804705 has 24 divisors (see below), whose sum is σ = 40703208. Its totient is φ = 10734336.

The previous prime is 21804701. The next prime is 21804719. The reversal of 21804705 is 50740812.

It can be written as a sum of positive squares in 4 ways, for example, as 1527696 + 20277009 = 1236^2 + 4503^2 .

It is not a de Polignac number, because 21804705 - 2² = 21804701 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21804701) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 18052 + ... + 19221.

It is an arithmetic number, because the mean of its divisors is an integer number (1695967).

Almost surely, 2^21804705 is an apocalyptic number.

It is an amenable number.

21804705 is a deficient number, since it is larger than the sum of its proper divisors (18898503).

21804705 is a wasteful number, since it uses less digits than its factorization.

21804705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37297 (or 37294 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 27.

The square root of 21804705 is about 4669.5508349305. The cubic root of 21804705 is about 279.3723398092.

The spelling of 21804705 in words is "twenty-one million, eight hundred four thousand, seven hundred five".