21735021 has 32 divisors (see below), whose sum is σ = 37122048. Its totient is φ = 10981440.

The previous prime is 21735011. The next prime is 21735029. The reversal of 21735021 is 12053712.

It is not a de Polignac number, because 21735021 - 2⁵ = 21734989 is a prime.

It is a super-2 number, since 2×21735021² = 944822275740882, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21735029) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 7276 + ... + 9818.

It is an arithmetic number, because the mean of its divisors is an integer number (1160064).

Almost surely, 2^21735021 is an apocalyptic number.

21735021 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21735021 is a deficient number, since it is larger than the sum of its proper divisors (15387027).

21735021 is a wasteful number, since it uses less digits than its factorization.

21735021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2601.

The product of its (nonzero) digits is 420, while the sum is 21.

The square root of 21735021 is about 4662.0833325886. The cubic root of 21735021 is about 279.0744139325.

Adding to 21735021 its reverse (12053712), we get a palindrome (33788733).

The spelling of 21735021 in words is "twenty-one million, seven hundred thirty-five thousand, twenty-one".