21971220 has 48 divisors (see below), whose sum is σ = 64760640. Its totient is φ = 5550336.

The previous prime is 21971197. The next prime is 21971221. The reversal of 21971220 is 2217912.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21971221) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8497 + ... + 10776.

It is an arithmetic number, because the mean of its divisors is an integer number (1349180).

Almost surely, 2^21971220 is an apocalyptic number.

21971220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21971220 is an abundant number, since it is smaller than the sum of its proper divisors (42789420).

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

21971220 is a wasteful number, since it uses less digits than its factorization.

21971220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19304 (or 19302 counting only the distinct ones).

The product of its (nonzero) digits is 504, while the sum is 24.

The square root of 21971220 is about 4687.3467974964. The cubic root of 21971220 is about 280.0816938495.

The spelling of 21971220 in words is "twenty-one million, nine hundred seventy-one thousand, two hundred twenty".