21209607 has 10 divisors (see below), whose sum is σ = 31683608. Its totient is φ = 14139684.

The previous prime is 21209603. The next prime is 21209609. The reversal of 21209607 is 70690212.

It is not a de Polignac number, because 21209607 - 2² = 21209603 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21209603) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 130843 + ... + 131004.

Almost surely, 2^21209607 is an apocalyptic number.

21209607 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

21209607 is a deficient number, since it is larger than the sum of its proper divisors (10474001).

21209607 is an equidigital number, since it uses as much as digits as its factorization.

21209607 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 261859 (or 261850 counting only the distinct ones).

The product of its (nonzero) digits is 1512, while the sum is 27.

The square root of 21209607 is about 4605.3889086591. The cubic root of 21209607 is about 276.8073008017.

Adding to 21209607 its reverse (70690212), we get a palindrome (91899819).

It can be divided in two parts, 21 and 209607, that added together give a triangular number (209628 = T₆₄₇).

The spelling of 21209607 in words is "twenty-one million, two hundred nine thousand, six hundred seven".