21979776 has 256 divisors, whose sum is σ = 78140160. Its totient is φ = 5308416.

The previous prime is 21979757. The next prime is 21979781. The reversal of 21979776 is 67797912.

It is a super-2 number, since 2×21979776² = 966221106020352, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (48).

It is a congruent number.

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, 594030 + ... + 594066.

It is an arithmetic number, because the mean of its divisors is an integer number (305235).

Almost surely, 2^21979776 is an apocalyptic number.

21979776 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21979776, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39070080).

21979776 is an abundant number, since it is smaller than the sum of its proper divisors (56160384).

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

21979776 is a wasteful number, since it uses less digits than its factorization.

21979776 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 91 (or 79 counting only the distinct ones).

The product of its digits is 333396, while the sum is 48.

The square root of 21979776 is about 4688.2593784901. The cubic root of 21979776 is about 280.1180454642.

It can be divided in two parts, 21 and 979776, that multiplied together give a square (20575296 = 4536²).

The spelling of 21979776 in words is "twenty-one million, nine hundred seventy-nine thousand, seven hundred seventy-six".