21977940 has 96 divisors (see below), whose sum is σ = 67495680. Its totient is φ = 5318656.

The previous prime is 21977933. The next prime is 21977941. The reversal of 21977940 is 4977912.

21977940 = T₁₆ + T₁₇ + ... + T₅₀₈.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21977941) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 29209 + ... + 29951.

It is an arithmetic number, because the mean of its divisors is an integer number (703080).

Almost surely, 2^21977940 is an apocalyptic number.

21977940 is a gapful number since it is divisible by the number (20) 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 21977940, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33747840).

21977940 is an abundant number, since it is smaller than the sum of its proper divisors (45517740).

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

21977940 is a wasteful number, since it uses less digits than its factorization.

21977940 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 801 (or 799 counting only the distinct ones).

The product of its (nonzero) digits is 31752, while the sum is 39.

The square root of 21977940 is about 4688.0635661219. The cubic root of 21977940 is about 280.1102457024.

The spelling of 21977940 in words is "twenty-one million, nine hundred seventy-seven thousand, nine hundred forty".