21073780 has 48 divisors (see below), whose sum is σ = 54472320. Its totient is φ = 6668928.

The previous prime is 21073739. The next prime is 21073799. The reversal of 21073780 is 8737012.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3970 + ... + 7609.

It is an arithmetic number, because the mean of its divisors is an integer number (1134840).

Almost surely, 2^21073780 is an apocalyptic number.

21073780 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21073780 is an abundant number, since it is smaller than the sum of its proper divisors (33398540).

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

21073780 is a wasteful number, since it uses less digits than its factorization.

21073780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11608 (or 11606 counting only the distinct ones).

The product of its (nonzero) digits is 2352, while the sum is 28.

The square root of 21073780 is about 4590.6186946859. The cubic root of 21073780 is about 276.2151406639.

The spelling of 21073780 in words is "twenty-one million, seventy-three thousand, seven hundred eighty".