21020637 has 16 divisors (see below), whose sum is σ = 30666240. Its totient is φ = 12702000.

The previous prime is 21020633. The next prime is 21020641. The reversal of 21020637 is 73602012.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21020633) and next prime (21020641).

It is not a de Polignac number, because 21020637 - 2² = 21020633 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21020633) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13762 + ... + 15212.

It is an arithmetic number, because the mean of its divisors is an integer number (1916640).

Almost surely, 2^21020637 is an apocalyptic number.

It is an amenable number.

21020637 is a deficient number, since it is larger than the sum of its proper divisors (9645603).

21020637 is a wasteful number, since it uses less digits than its factorization.

21020637 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1904.

The product of its (nonzero) digits is 504, while the sum is 21.

The square root of 21020637 is about 4584.8268233380. The cubic root of 21020637 is about 275.9827625235.

Adding to 21020637 its reverse (73602012), we get a palindrome (94622649).

The spelling of 21020637 in words is "twenty-one million, twenty thousand, six hundred thirty-seven".