21575137 has 6 divisors (see below), whose sum is σ = 21858018. Its totient is φ = 21295872.

The previous prime is 21575129. The next prime is 21575149. The reversal of 21575137 is 73157512.

It can be written as a sum of positive squares in only one way, i.e., 12082576 + 9492561 = 3476^2 + 3081^2 .

It is not a de Polignac number, because 21575137 - 2³ = 21575129 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21575099 and 21575108.

It is not an unprimeable number, because it can be changed into a prime (21575117) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 4513 + ... + 7969.

It is an arithmetic number, because the mean of its divisors is an integer number (3643003).

Almost surely, 2^21575137 is an apocalyptic number.

It is an amenable number.

21575137 is a deficient number, since it is larger than the sum of its proper divisors (282881).

21575137 is an frugal number, since it uses more digits than its factorization.

21575137 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3615 (or 3536 counting only the distinct ones).

The product of its digits is 7350, while the sum is 31.

The square root of 21575137 is about 4644.9044123642. The cubic root of 21575137 is about 278.3884335995.

It can be divided in two parts, 21575 and 137, that added together give a palindrome (21712).

The spelling of 21575137 in words is "twenty-one million, five hundred seventy-five thousand, one hundred thirty-seven".