21957780 has 48 divisors (see below), whose sum is σ = 66213504. Its totient is φ = 5404800.

The previous prime is 21957779. The next prime is 21957781. The reversal of 21957780 is 8775912.

It is an interprime number because it is at equal distance from previous prime (21957779) and next prime (21957781).

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21957781) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13296 + ... + 14855.

It is an arithmetic number, because the mean of its divisors is an integer number (1379448).

Almost surely, 2^21957780 is an apocalyptic number.

21957780 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21957780 is an abundant number, since it is smaller than the sum of its proper divisors (44255724).

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

21957780 is a wasteful number, since it uses less digits than its factorization.

21957780 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28176 (or 28174 counting only the distinct ones).

The product of its (nonzero) digits is 35280, while the sum is 39.

The square root of 21957780 is about 4685.9129313294. The cubic root of 21957780 is about 280.0245726734.

The spelling of 21957780 in words is "twenty-one million, nine hundred fifty-seven thousand, seven hundred eighty".