21477780 has 36 divisors (see below), whose sum is σ = 65149812. Its totient is φ = 5727360.

The previous prime is 21477763. The next prime is 21477793. The reversal of 21477780 is 8777412.

It can be written as a sum of positive squares in 2 ways, for example, as 13793796 + 7683984 = 3714^2 + 2772^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a super-2 number, since 2×21477780² = 922590067456800, which contains 22 as substring.

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

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 59481 + ... + 59840.

It is an arithmetic number, because the mean of its divisors is an integer number (1809717).

Almost surely, 2^21477780 is an apocalyptic number.

21477780 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21477780 is an abundant number, since it is smaller than the sum of its proper divisors (43672032).

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

21477780 is a wasteful number, since it uses less digits than its factorization.

21477780 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 119336 (or 119331 counting only the distinct ones).

The product of its (nonzero) digits is 21952, while the sum is 36.

The square root of 21477780 is about 4634.4125841362. The cubic root of 21477780 is about 277.9690630308.

The spelling of 21477780 in words is "twenty-one million, four hundred seventy-seven thousand, seven hundred eighty".