21780273 has 8 divisors (see below), whose sum is σ = 29201536. Its totient is φ = 14439600.

The previous prime is 21780257. The next prime is 21780329. The reversal of 21780273 is 37208712.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21780273 - 2⁴ = 21780257 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21780273.

It is not an unprimeable number, because it can be changed into a prime (21780203) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19513 + ... + 20598.

It is an arithmetic number, because the mean of its divisors is an integer number (3650192).

Almost surely, 2^21780273 is an apocalyptic number.

It is an amenable number.

21780273 is a deficient number, since it is larger than the sum of its proper divisors (7421263).

21780273 is a wasteful number, since it uses less digits than its factorization.

21780273 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40295.

The product of its (nonzero) digits is 4704, while the sum is 30.

The square root of 21780273 is about 4666.9340042473. The cubic root of 21780273 is about 279.2679559779.

Adding to 21780273 its reverse (37208712), we get a palindrome (58988985).

The spelling of 21780273 in words is "twenty-one million, seven hundred eighty thousand, two hundred seventy-three".