21497760 has 72 divisors (see below), whose sum is σ = 73366020. Its totient is φ = 5732352.

The previous prime is 21497731. The next prime is 21497761. The reversal of 21497760 is 6779412.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 21123216 + 374544 = 4596^2 + 612^2 .

It is a tau number, because it is divible by the number of its divisors (72).

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21497761) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6025 + ... + 8904.

Almost surely, 2^21497760 is an apocalyptic number.

21497760 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21497760 is an abundant number, since it is smaller than the sum of its proper divisors (51868260).

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

21497760 is a wasteful number, since it uses less digits than its factorization.

21497760 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14950 (or 14939 counting only the distinct ones).

The product of its (nonzero) digits is 21168, while the sum is 36.

The square root of 21497760 is about 4636.5676960441. The cubic root of 21497760 is about 278.0552311635.

The spelling of 21497760 in words is "twenty-one million, four hundred ninety-seven thousand, seven hundred sixty".