21542737 has 12 divisors (see below), whose sum is σ = 23057460. Its totient is φ = 20102880.

The previous prime is 21542687. The next prime is 21542761. The reversal of 21542737 is 73724512.

It can be written as a sum of positive squares in 2 ways, for example, as 5550736 + 15992001 = 2356^2 + 3999^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21542737 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (31).

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21542699 and 21542708.

It is not an unprimeable number, because it can be changed into a prime (21542767) 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, 27483 + ... + 28255.

It is an arithmetic number, because the mean of its divisors is an integer number (1921455).

Almost surely, 2^21542737 is an apocalyptic number.

It is an amenable number.

21542737 is a deficient number, since it is larger than the sum of its proper divisors (1514723).

21542737 is an equidigital number, since it uses as much as digits as its factorization.

21542737 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 864 (or 833 counting only the distinct ones).

The product of its digits is 11760, while the sum is 31.

The square root of 21542737 is about 4641.4154091182. The cubic root of 21542737 is about 278.2490091607.

The spelling of 21542737 in words is "twenty-one million, five hundred forty-two thousand, seven hundred thirty-seven".