21260778 has 64 divisors (see below), whose sum is σ = 56153088. Its totient is φ = 5195520.

The previous prime is 21260749. The next prime is 21260797. The reversal of 21260778 is 87706212.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 6501 + ... + 9207.

It is an arithmetic number, because the mean of its divisors is an integer number (877392).

Almost surely, 2^21260778 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21260778, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28076544).

21260778 is an abundant number, since it is smaller than the sum of its proper divisors (34892310).

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

21260778 is a wasteful number, since it uses less digits than its factorization.

21260778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2747.

The product of its (nonzero) digits is 9408, while the sum is 33.

The square root of 21260778 is about 4610.9411186872. The cubic root of 21260778 is about 277.0297335006.

The spelling of 21260778 in words is "twenty-one million, two hundred sixty thousand, seven hundred seventy-eight".