20401531 has 4 divisors (see below), whose sum is σ = 20483064. Its totient is φ = 20320000.

The previous prime is 20401523. The next prime is 20401553. The reversal of 20401531 is 13510402.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20401531 - 2³ = 20401523 is a prime.

It is a super-2 number, since 2×20401531² = 832444934287922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20401501) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 40390 + ... + 40891.

It is an arithmetic number, because the mean of its divisors is an integer number (5120766).

Almost surely, 2^20401531 is an apocalyptic number.

20401531 is a deficient number, since it is larger than the sum of its proper divisors (81533).

20401531 is an equidigital number, since it uses as much as digits as its factorization.

20401531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81532.

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 20401531 is about 4516.8053976234. The cubic root of 20401531 is about 273.2462768892.

Adding to 20401531 its reverse (13510402), we get a palindrome (33911933).

The spelling of 20401531 in words is "twenty million, four hundred one thousand, five hundred thirty-one".