21315220776 has 96 divisors (see below), whose sum is σ = 59384599560. Its totient is φ = 6901894656.

The previous prime is 21315220769. The next prime is 21315220783. The reversal of 21315220776 is 67702251312.

It is an interprime number because it is at equal distance from previous prime (21315220769) and next prime (21315220783).

It can be written as a sum of positive squares in 4 ways, for example, as 19301544900 + 2013675876 = 138930^2 + 44874^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 21315220776.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1733466 + ... + 1745718.

Almost surely, 2^21315220776 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21315220776, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29692299780).

21315220776 is an abundant number, since it is smaller than the sum of its proper divisors (38069378784).

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

21315220776 is a wasteful number, since it uses less digits than its factorization.

21315220776 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12955 (or 12948 counting only the distinct ones).

The product of its (nonzero) digits is 35280, while the sum is 36.

The spelling of 21315220776 in words is "twenty-one billion, three hundred fifteen million, two hundred twenty thousand, seven hundred seventy-six".