21997960 has 16 divisors (see below), whose sum is σ = 49495500. Its totient is φ = 8799168.

The previous prime is 21997957. The next prime is 21997981. The reversal of 21997960 is 6979912.

It can be written as a sum of positive squares in 2 ways, for example, as 21288996 + 708964 = 4614^2 + 842^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 274935 + ... + 275014.

Almost surely, 2^21997960 is an apocalyptic number.

21997960 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21997960 is an abundant number, since it is smaller than the sum of its proper divisors (27497540).

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

21997960 is a wasteful number, since it uses less digits than its factorization.

21997960 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 549960 (or 549956 counting only the distinct ones).

The product of its (nonzero) digits is 61236, while the sum is 43.

The square root of 21997960 is about 4690.1982900513. The cubic root of 21997960 is about 280.1952719490.

The spelling of 21997960 in words is "twenty-one million, nine hundred ninety-seven thousand, nine hundred sixty".