21051630 has 32 divisors (see below), whose sum is σ = 56138400. Its totient is φ = 5613696.

The previous prime is 21051623. The next prime is 21051637. The reversal of 21051630 is 3615012.

It is an interprime number because it is at equal distance from previous prime (21051623) and next prime (21051637).

It is a super-2 number, since 2×21051630² = 886342251313800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21051637) 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, 38715 + ... + 39254.

It is an arithmetic number, because the mean of its divisors is an integer number (1754325).

Almost surely, 2^21051630 is an apocalyptic number.

21051630 is an abundant number, since it is smaller than the sum of its proper divisors (35086770).

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

21051630 is a wasteful number, since it uses less digits than its factorization.

21051630 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 77985 (or 77979 counting only the distinct ones).

The product of its (nonzero) digits is 180, while the sum is 18.

The square root of 21051630 is about 4588.2055315777. The cubic root of 21051630 is about 276.1183330012.

Adding to 21051630 its reverse (3615012), we get a palindrome (24666642).

The spelling of 21051630 in words is "twenty-one million, fifty-one thousand, six hundred thirty".